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More evidence for groundwater on Mars

Image credit: NASA / USGS

Image credit: NASA / USGS

Monica Pondrelli and colleagues investigated the Equatorial Layered Deposits (ELDs) of Arabia Terra in Firsoff crater area, Mars, to understand their formation and potential habitability. On the plateau, ELDs consist of rare mounds, flat-lying deposits, and cross-bedded dune fields. Pondrelli and colleagues interpret the mounds as smaller spring deposits, the flat-lying deposits as playa, and the cross-bedded dune fields as aeolian. They write that groundwater fluctuations appear to be the major factor controlling ELD deposition.

Pondrelli and colleagues also note that the ELDs inside the craters would likely have originated by fluid upwelling through the fissure ridges and the mounds, and that lead to evaporite precipitation. The presence of spring and playa deposits points to the possible presence of a hydrological cycle, driving groundwater upwelling on Mars at surface temperatures above freezing. Pondrelli and colleagues write that such conditions in a similar Earth environment would have been conducive for microbial colonization.

As a basis for their research, Pondrelli and colleagues produced a detailed geological map of the Firsoff crater area. The new map includes crater count dating, a survey of the stratigraphic relations, and analysis of the depositional geometries and compositional constraints. They note that this ELD unit consists of sulfates and shows other characteristics typical of evaporites such as polygonal pattern and indications of dissolution.

Reference: Equatorial layered deposits in Arabia Terra, Mars: Facies and process variability.  M. Pondrelli et al., International Research School of Planetary Sciences, Università d’Annunzio, Pescara, Italy. Published online ahead of print on 10 Mar. 2015; http://dx.doi.org/10.1130/B31225.1.

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Ancient Martian lake system records 2 water-related events

A false-color topographic map (blue marks low elevations) shows the area around Mars's Jezero Crater, which was home to an ancient lake system. New research shows that the region around Jezero hosted at least two separate episodes of water activity. Credit: NASA/MSSS/ASU/GSFC

A false-color topographic map (blue marks low elevations) shows the area around Mars’s Jezero Crater, which was home to an ancient lake system. New research shows that the region around Jezero hosted at least two separate episodes of water activity. Credit: NASA/MSSS/ASU/GSFC

Researchers from Brown University have completed a new analysis of an ancient Martian lake system in Jezero Crater, near the planet’s equator. The study finds that the onslaught of water that filled the crater was one of at least two separate periods of water activity in the region surrounding Jezero.

“We can say that this one really well-exposed location makes a strong case for at least two periods of water-related activity in Mars’ history,” said Tim Goudge, a graduate student at Brown who led the work. “That tells us something really interesting about how early Mars operated.”

The study is in press in the Journal of Geophysical Research: Planets.

The ancient lake at Jezero crater was first identified in 2005 by Caleb Fassett, a former Brown graduate student now a professor at Mount Holyoke College. Fassett identified two channels on the northern and western sides of the crater that appear to have supplied it with water. That water eventually overtopped the crater wall on the southern side and flowed out through a third large channel. It’s not clear how long the system was active, but seems to have dried out around 3.5 to 3.8 billion years ago.

Each of the crater’s inlet channels has a delta-like deposit where sediment carried by water was deposited in the lake. In 2008, Bethany Ehlmann, another former Brown graduate student now a professor at Caltech, showed that those fan deposits are full of clay minerals — a clear sign of alteration by water. The question of how exactly those minerals formed, however, remained open. Did the minerals form in place in the lake, or did they form elsewhere and get transported into the lake?

That’s the question Goudge and his colleagues wanted to answer.

To do that, Goudge gathered high-resolution orbital images from NASA’s CTX instrument, and combined them with data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard NASA’s Mars Reconnaissance Orbiter. Using those two sources, Goudge put together a detailed geological and mineralogical map of the entire Jezero Crater paleolake system.

The map showed that each of the fan deposits has its own distinct mineral signature that matches the signature of the watershed from which it was sourced. “That’s a good indication that the minerals formed in the watershed and were then transported into the lake,” Goudge said.

The minerals’ formation and their transportation seem to have been separated by a fair amount of time. Mapping of the watershed showed a younger layer of rock that sits on top of the hydrated minerals. The crater’s inlet channels cut through that layer of younger rock. That means the water that carved the channels must have flowed well after the mineral layer had formed.

A delta-like fan at the western edge of Jezero Crater marks an area where flowing water would have entered the lake-filled crater and deposited clay minerals transported from the surrounding watershed. Image: NASA/MSSS

A delta-like fan at the western edge of Jezero Crater marks an area where flowing water would have entered the lake-filled crater and deposited clay minerals transported from the surrounding watershed. Image: NASA/MSSS

“What it implies is that there were actually two periods of water-related activity,” Goudge said. “The earlier episode formed the alteration minerals in the watershed, then some time later you had the surface water activity that transported the minerals into the lake. At this site, those two events appear not to have been genetically related.”

That finding could shed light on the water story for early Mars. It’s clear that Mars was once much wetter than it is now, but it’s not clear that the Martian climate was warm enough to sustain liquid water at the surface for long periods. Some researchers have suggested that if the early Martian climate was cold, chemical alteration on Mars may have been driven largely by water percolating in the warmer subsurface crust. That period of subsurface activity was followed some time later by pulses of water on the surface — potentially sourced by either snowmelt or rainfall — during transient periods of warm temperatures. That second round of events was largely responsible for the mechanical erosion on the Martian surface.

The events at Jezero seem to be consistent with that idea, the researchers say.

The fact that Jezero crater records the history of two separate water events makes it an interesting target for future study. In fact, Jezero is high on scientists’ list of possible landing sites for NASA’s Mars 2020 rover. If life had emerged in either of the two water-related events, signs of it may well have been preserved at Jezero.

“River and lake deposits on Earth are some of the best preservers of biologic signatures,” Goudge said. “At Jezero, you’re gathering all this material from this huge watershed and dumping into one place. So if there perhaps was any biologic or organic material in the watershed, you might have transported some of that to the basin.”

The water that stood in the lake from the second event does not seem to have chemically altered the rock much at all, the new study shows. That helps confirm what previous researchers had suspected: that Jezero was filled with fairly fresh water with a nearly neutral pH — making it a potentially habitable environment.

NASA held a workshop last May to start the process of selecting sites for the 2020 rover. Goudge and his colleagues gave a presentation making the case for Jezero, and the scientists in attendance voted it as one of the top five landing site candidates. There are several more rounds of the selection process to go, and Goudge hopes Jezero will stay in contention.

“We think Jezero has a really interesting story to tell,” Goudge said. “It would be a fun place to get to drive around in.”

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NASA Announces Next Steps on Journey to Mars: Progress on Asteroid Initiative

The Asteroid Redirect Vehicle, part of NASA's Asteroid Initiative concept, is shown traveling to lunar orbit using its solar electric propulsion system in this artist's concept. Image credit: NASA

The Asteroid Redirect Vehicle, part of NASA’s Asteroid Initiative concept, is shown traveling to lunar orbit using its solar electric propulsion system in this artist’s concept. Image credit: NASA

NASA Wednesday announced more details in its plan for its Asteroid Redirect Mission (ARM), which in the mid-2020s will test a number of new capabilities needed for future human expeditions to deep space, including to Mars. NASA also announced it has increased the detection of near-Earth Asteroids by 65 percent since launching its asteroid initiative three years ago.

For ARM, a robotic spacecraft will capture a boulder from the surface of a near-Earth asteroid and move it into a stable orbit around the moon for exploration by astronauts, all in support of advancing the nation’s journey to Mars.

“The Asteroid Redirect Mission will provide an initial demonstration of several spaceflight capabilities we will need to send astronauts deeper into space, and eventually, to Mars,” said NASA Associate Administrator Robert Lightfoot. “The option to retrieve a boulder from an asteroid will have a direct impact on planning for future human missions to deep space and begin a new era of spaceflight.”

The agency plans to announce the specific asteroid selected for the mission no earlier than 2019, approximately a year before launching the robotic spacecraft. Before an asteroid is considered a valid candidate for the mission, scientists must first determine its characteristics, in addition to size, such as rotation, shape and precise orbit. NASA has identified three valid candidates for the mission so far: Itokawa, Bennu and 2008 EV5. The agency expects to identify one or two additional candidates each year leading up to the mission.

Following its rendezvous with the target asteroid, the uncrewed ARM spacecraft will deploy robotic arms to capture a boulder from its surface. It then will begin a multi-year journey to redirect the boulder into orbit around the moon.

Throughout its mission, the ARM robotic spacecraft will test a number of capabilities needed for future human missions, including advanced Solar Electric Propulsion (SEP), a valuable capability that converts sunlight to electrical power through solar arrays and then uses the resulting power to propel charged atoms to move a spacecraft. This method of propulsion can move massive cargo very efficiently. While slower than conventional chemical rocket propulsion, SEP-powered spacecraft require significantly less propellant and fewer launches to support human exploration missions, which could reduce costs.

Future SEP-powered spacecraft could pre-position cargo or vehicles for future human missions into deep space, either awaiting crews at Mars or staged around the moon as a waypoint for expeditions to the Red Planet.

ARM’s SEP-powered robotic spacecraft will test new trajectory and navigation techniques in deep space, working with the moon’s gravity to place the asteroid in a stable lunar orbit called a distant retrograde orbit. This is a suitable staging point for astronauts to rendezvous with a deep space habitat that will carry them to Mars.

Before the piece of the asteroid is moved to lunar orbit, NASA will use the opportunity to test planetary defense techniques to help mitigate potential asteroid impact threats in the future. The experience and knowledge acquired through this operation will help NASA develop options to move an asteroid off an Earth-impacting course, if and when that becomes necessary.

In 2005, NASA’s Deep Impact comet science mission tested technology that could assist in changing the course of a near-Earth object using a direct hit with a spacecraft. The ARM robotic spacecraft opens a new and second option for planetary defense using a technique called a gravity tractor. All mass exerts and experiences gravity and, in space, the gravitational attraction even between masses of modest size can significantly affect their motion. This means that by rendezvousing with the asteroid and holding a halo orbit in the appropriate direction, the ARM robotic spacecraft can slowly pull the asteroid without touching it. The effectiveness of this maneuver is increased, moreover, if mass is moved from the asteroid to the spacecraft by the capture of a boulder.

It will take approximately six years for the ARM robotic spacecraft to move the asteroid mass into lunar orbit. In the mid-2020s, NASA’s Orion spacecraft will launch on the agency’s Space Launch System rocket, carrying astronauts on a mission to rendezvous with and explore the asteroid mass. The current concept for the crewed mission component of ARM is a two-astronaut, 24-25 day mission.

This crewed mission will further test many capabilities needed to advance human spaceflight for deep space missions to Mars and elsewhere, including new sensor technologies and a docking system that will connect Orion to the robotic spacecraft carrying the asteroid mass. Astronauts will conduct spacewalks outside Orion to study and collect samples of the asteroid boulder wearing new spacesuits designed for deep space missions.

Collecting these samples will help astronauts and mission managers determine how best to secure and safely return samples from future Mars missions. And, because asteroids are made of remnants from the formation of the solar system, the returned samples could provide valuable data for scientific research or commercial entities interested in asteroid mining as a future resources.

In 2012, the president’s NASA budget included, and Congress authorized, $20.4 million for an expanded NASA Near-Earth Object (NEO) Observations Program, increasing the resources for this critical program from the $4 million per year it had received since the 1990s. The program was again expanded in fiscal year 2014, with a budget of $40.5 million. NASA is asking Congress for $50 million for this important work in the 2016 budget.

“Asteroids are a hot topic,” said Jim Green, director of NASA Planetary Science. “Not just because they could pose a threat to Earth, but also for their scientific value and NASA’s planned mission to one as a stepping stone to Mars.”

NASA has identified more than 12,000 NEOs to date, including 96 percent of near-Earth asteroids larger than 0.6 miles (1 kilometer) in size. NASA has not detected any objects of this size that pose an impact hazard to Earth in the next 100 years. Smaller asteroids do pass near Earth, however, and some could pose an impact threat. In 2011, 893 near-Earth asteroids were found. In 2014, that number was increased to 1,472.

In addition to NASA’s ongoing work detecting and cataloging asteroids, the agency has engaged the public in the hunt for these space rocks through the agency’s Asteroid Grand Challenge activities, including prize competitions. During the recent South by Southwest Festival in Austin, Texas, the agency announced the release of a software application based on an algorithm created by a NASA challenge that has the potential to increase the number of new asteroid discoveries by amateur astronomers.

More information about the Asteroid Redirect Mission, visit: http://www.nasa.gov/asteroidinitiative

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New Research Suggests Solar System May Have Once Harbored Super-Earths

This snapshot from a new simulation depicts a time early in the solar system's history when Jupiter likely made a grand inward migration (here, Jupiter's orbit is the thick white circle). As it moved inward, Jupiter picked up primitive planetary building blocks, or planetesimals, and drove them into eccentric orbits (turquoise) that overlapped the unperturbed part of the planetary disk (yellow), setting off a cascade of collisions that would have ushered any interior planets into the sun. Credit: K.Batygin/Caltech

This snapshot from a new simulation depicts a time early in the solar system’s history when Jupiter likely made a grand inward migration (here, Jupiter’s orbit is the thick white circle). As it moved inward, Jupiter picked up primitive planetary building blocks, or planetesimals, and drove them into eccentric orbits (turquoise) that overlapped the unperturbed part of the planetary disk (yellow), setting off a cascade of collisions that would have ushered any interior planets into the sun.
Credit: K.Batygin/Caltech

Long before Mercury, Venus, Earth, and Mars formed, it seems that the inner solar system may have harbored a number of super-Earths—planets larger than Earth but smaller than Neptune. If so, those planets are long gone—broken up and fallen into the sun billions of years ago largely due to a great inward-and-then-outward journey that Jupiter made early in the solar system’s history.

This possible scenario has been suggested by Konstantin Batygin, a Caltech planetary scientist, and Gregory Laughlin of UC Santa Cruz in a paper that appears the week of March 23 in the online edition of the Proceedings of the National Academy of Sciences (PNAS). The results of their calculations and simulations suggest the possibility of a new picture of the early solar system that would help to answer a number of outstanding questions about the current makeup of the solar system and of Earth itself. For example, the new work addresses why the terrestrial planets in our solar system have such relatively low masses compared to the planets orbiting other sun-like stars.

“Our work suggests that Jupiter’s inward-outward migration could have destroyed a first generation of planets and set the stage for the formation of the mass-depleted terrestrial planets that our solar system has today,” says Batygin, an assistant professor of planetary science. “All of this fits beautifully with other recent developments in understanding how the solar system evolved, while filling in some gaps.”

Thanks to recent surveys of exoplanets—planets in solar systems other than our own—we know that about half of sun-like stars in our galactic neighborhood have orbiting planets. Yet those systems look nothing like our own. In our solar system, very little lies within Mercury’s orbit; there is only a little debris—probably near-Earth asteroids that moved further inward—but certainly no planets. That is in sharp contrast with what astronomers see in most planetary systems. These systems typically have one or more planets that are substantially more massive than Earth orbiting closer to their suns than Mercury does, but very few objects at distances beyond.

“Indeed, it appears that the solar system today is not the common representative of the galactic planetary census. Instead we are something of an outlier,” says Batygin. “But there is no reason to think that the dominant mode of planet formation throughout the galaxy should not have occurred here. It is more likely that subsequent changes have altered its original makeup.”

According to Batygin and Laughlin, Jupiter is critical to understanding how the solar system came to be the way it is today. Their model incorporates something known as the Grand Tack scenario, which was first posed in 2001 by a group at Queen Mary University of London and subsequently revisited in 2011 by a team at the Nice Observatory.

That scenario says that during the first few million years of the solar system’s lifetime, when planetary bodies were still embedded in a disk of gas and dust around a relatively young sun, Jupiter became so massive and gravitationally influential that it was able to clear a gap in the disk. And as the sun pulled the disk’s gas in toward itself, Jupiter also began drifting inward, as though carried on a giant conveyor belt.

The artist's concept depicts Kepler-69c, a super-Earth-size planet in the habitable zone of a star like our sun. Image credit: NASA Ames/JPL-Caltech

The artist’s concept depicts Kepler-69c, a super-Earth-size planet in the habitable zone of a star like our sun.
Image credit: NASA Ames/JPL-Caltech

“Jupiter would have continued on that belt, eventually being dumped onto the sun if not for Saturn,” explains Batygin. Saturn formed after Jupiter but got pulled toward the sun at a faster rate, allowing it to catch up. Once the two massive planets got close enough, they locked into a special kind of relationship called an orbital resonance, where their orbital periods were rational—that is, expressible as a ratio of whole numbers. In a 2:1 orbital resonance, for example, Saturn would complete two orbits around the sun in the same amount of time that it took Jupiter to make a single orbit. In such a relationship, the two bodies would begin to exert a gravitational influence on one another.

“That resonance allowed the two planets to open up a mutual gap in the disk, and they started playing this game where they traded angular momentum and energy with one another, almost to a beat,” says Batygin. Eventually, that back and forth would have caused all of the gas between the two worlds to be pushed out, a situation that would have reversed the planets’ migration direction and sent them back outward in the solar system. (Hence, the “tack” part of the Grand Tack scenario: the planets migrate inward and then change course dramatically, something like a boat tacking around a buoy.)

In an earlier model developed by Bradley Hansen at UCLA, the terrestrial planets conveniently end up in their current orbits with their current masses under a particular set of circumstances—one in which all of the inner solar system’s planetary building blocks, or planetesimals, happen to populate a narrow ring stretching from 0.7 to 1 astronomical unit (1 astronomical unit is the average distance from the sun to Earth), 10 million years after the sun’s formation. According to the Grand Tack scenario, the outer edge of that ring would have been delineated by Jupiter as it moved toward the sun on its conveyor belt and cleared a gap in the disk all the way to Earth’s current orbit.

But what about the inner edge? Why should the planetesimals be limited to the ring on the inside? “That point had not been addressed,” says Batygin.

He says the answer could lie in primordial super-Earths. The empty hole of the inner solar system corresponds almost exactly to the orbital neighborhood where super-Earths are typically found around other stars. It is therefore reasonable to speculate that this region was cleared out in the primordial solar system by a group of first-generation planets that did not survive.

Batygin and Laughlin’s calculations and simulations show that as Jupiter moved inward, it pulled all the planetesimals it encountered along the way into orbital resonances and carried them toward the sun. But as those planetesimals got closer to the sun, their orbits also became elliptical.

“You cannot reduce the size of your orbit without paying a price, and that turns out to be increased ellipticity,” explains Batygin. Those new, more elongated orbits caused the planetesimals, mostly on the order of 100 kilometers in radius, to sweep through previously unpenetrated regions of the disk, setting off a cascade of collisions among the debris. In fact, Batygin’s calculations show that during this period, every planetesimal would have collided with another object at least once every 200 years, violently breaking them apart and sending them decaying into the sun at an increased rate.

The researchers did one final simulation to see what would happen to a population of super-Earths in the inner solar system if they were around when this cascade of collisions started. They ran the simulation on a well-known extrasolar system known as Kepler-11, which features six super-Earths with a combined mass 40 times that of Earth, orbiting a sun-like star. The result? The model predicts that the super-Earths would be shepherded into the sun by a decaying avalanche of planetesimals over a period of 20,000 years.

Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist's conception of a simultaneous transit of three planets observed by NASA's Kepler spacecraft on Aug. 26, 2010. Image credit: NASA/Tim Pyle

Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist’s conception of a simultaneous transit of three planets observed by NASA’s Kepler spacecraft on Aug. 26, 2010. Image credit: NASA/Tim Pyle

“It’s a very effective physical process,” says Batygin. “You only need a few Earth masses worth of material to drive tens of Earth masses worth of planets into the sun.”

Batygin notes that when Jupiter tacked around, some fraction of the planetesimals it was carrying with it would have calmed back down into circular orbits. Only about 10 percent of the material Jupiter swept up would need to be left behind to account for the mass that now makes up Mercury, Venus, Earth, and Mars.

From that point, it would take millions of years for those planetesimals to clump together and eventually form the terrestrial planets—a scenario that fits nicely with measurements that suggest that Earth formed 100–200 million years after the birth of the sun. Since the primordial disk of hydrogen and helium gas would have been long gone by that time, this could also explain why Earth lacks a hydrogen atmosphere. “We formed from this volatile-depleted debris,” says Batygin.

And that sets us apart in another way from the majority of exoplanets. Batygin expects that most exoplanets—which are mostly super-Earths—have substantial hydrogen atmospheres, because they formed at a point in the evolution of their planetary disk when the gas would have still been abundant. “Ultimately, what this means is that planets truly like Earth are intrinsically not very common,” he says.

The paper also suggests that the formation of gas giant planets such as Jupiter and Saturn—a process that planetary scientists believe is relatively rare—plays a major role in determining whether a planetary system winds up looking something like our own or like the more typical systems with close-in super-Earths. As planet hunters identify additional systems that harbor gas giants, Batygin and Laughlin will have more data against which they can check their hypothesis—to see just how often other migrating giant planets set off collisional cascades in their planetary systems, sending primordial super-Earths into their host stars.

The researchers describe their work in a paper titled “Jupiter’s Decisive Role in the Inner Solar System’s Early Evolution.”

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Unexplained warm layer discovered in Venus’ atmosphere

Image Credit: ESA

Venus clouds. Image Credit: ESA

A group of Russian, European and American scientists have found a warm layer in Venus’ atmosphere, the nature of which is still unknown. The researchers made the discovery when compiling a temperature map of the upper atmosphere on the planet’s night side based on the data collected by the Venus Express probe.

“We measured temperatures at altitudes of 90 to 140 kilometers,” says an author of the study, Denis Belyaevof MIPT and the Space Research Institute of the Russian Academy of Sciences. “On the night side of the planet, temperatures normally fall with altitude, but we noticed a peak in the chart in the 90 to 100 kilometer range. Here, the atmosphere was 20-40 degrees warmer than we expected. We don’t yet understand what causes the warming, but Venus’ ozone layer is at this altitude. There may be a connection.”

Belyaev, along with his colleagues from MIPT and the Space Research Institute, Anna Fedorova and Oleg Korablev, and researchers from the French laboratory LATMOS, as well as from Belgium, Germany and the U.S. analyzed the data obtained by the SPICAV spectrometer on board Venus Express between June 2006 and February 2013.

The European mission Venus Express was launched from the Baikonur space center in 2005 using the Russian rocket Soyuz-FG. Scientific instruments for the probe were developed by an international team of scientists, including from Russia. The unit was removed from service in February 2015, but scientists continue to analyze the data it obtained throughout its operation.

SPICAV system (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus). Credit: Denis Belyaev, MIPT

SPICAV system (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus). Credit: Denis Belyaev, MIPT

The SPICAV system (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus) consisted of two spectrometers, an infrared one, created by Russian specialists, and an ultraviolet one, made by French scientists.

Atmospheric temperatures were taken in the UV channel using the stellar occultation method, wherein a spectrometer captures the light emitted by a star as it goes behind a planet. The starlight radiates through the planet’s atmosphere, whose characteristics can be retrieved based on the spectrum produced.

The scientists selected stars that shine brighter in ultraviolet, that is, from118 to 320 nanometers, the working range of the spectrometer (there were a total of 50 of them). Each second within the few minutes that the star took to disappear behind the planet’s horizon the spectrometer took a shot of its spectrum. Then the scientists divided the “atmospheric” spectrum by the star’s “clean” spectrum to determine the gas composition and density of the atmosphere at different altitudes, as well as temperatures. From June 2006 to February 2013 they made 587 “shots” of the atmosphere, which covered almost the entire night hemisphere.

“In almost every session of these seven years we detected a layer at altitudes of 90-100 km that is 20-40 kelvins warmer than it should be,” says Belyaev. “The air temperatures at these altitudesare220-240 kelvins, while they should be under 200.”

According to Belyaev, this layer is in the same range of altitudes where the ozone is. “We are carrying out correlation analysis to determine if these are connected or not,” Belyaev said. “We can’t rule out that this phenomenon may be explained by chemical reactions, namely the decomposition of ozone when it comes in contact with chlorine-based substances – these reactions may result in the release of heat.”

These are temperatures on the night side of Venus at altitudes of 90 and 100 km. Credit: Denis Belyaev, MIPT

These are temperatures on the night side of Venus at altitudes of 90 and 100 km. Credit: Denis Belyaev, MIPT

The researchers have found yet another peculiarity of Venus’ upper atmosphere: early in the morning it is warmer than in the evening, while it should be the other way round.

Venus is a unique planet in that rotates not in the direction of its movement along the circumsolar orbit, but in the opposite direction, because its rotation axis is tilted 177 degrees. And it rotates very slowly – a solar day on the planet lasts 116 days. During the long night the upper atmosphere cools, so at night it should be warmer than in the morning.

“We found that the atmospheric temperature is 20 degrees warmer in the morning than in the evening,” Belyaev says. “This is probably due to the global circulation of the atmosphere. The transition of the sub-solar point to the anti-solar point takes place at altitudes of about 100 kilometers. In this area on the night side, the air mass goes down to 70 km, which may lead to the adiabatic heating of the atmosphere.”

Article: Piccialli, A., et al., Thermal structure of Venus nightside upper atmosphere measured by stellar occultations with SPICAV/VenusExpress. Planetary and Space Science (DOI: 10.1016/j.pss.2014.12.009i)

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Explosions of Jupiter’s aurora linked to extraordinary planet-moon interaction

In this artist's rendering, flows of electrically charged ions and electrons accelerate along Jupiter's magnetic field lines (fountain-like blue curves), triggering auroras (blue rings) at the planet's pole. Accelerated particles come from clouds of material (red) spewed from volcanoes on Jupiter's moon Io (small orb to right). Recent observations of extreme ultraviolet emissions from Jupiter by satellite Hisaki (left foreground) and the Hubble Space Telescope (right) show episodes of sudden brightening of the planet's auroras. Interactions with the excited particles from Io likely also fuel these auroral explosions, new research shows, not interactions with particles from the Sun. Credit: Japan Aerospace Exploration Agency

In this artist’s rendering, flows of electrically charged ions and electrons accelerate along Jupiter’s magnetic field lines (fountain-like blue curves), triggering auroras (blue rings) at the planet’s pole. Accelerated particles come from clouds of material (red) spewed from volcanoes on Jupiter’s moon Io (small orb to right). Recent observations of extreme ultraviolet emissions from Jupiter by satellite Hisaki (left foreground) and the Hubble Space Telescope (right) show episodes of sudden brightening of the planet’s auroras. Interactions with the excited particles from Io likely also fuel these auroral explosions, new research shows, not interactions with particles from the Sun. Credit: Japan Aerospace Exploration Agency

On Earth, bursts of particles spewed by the Sun spark shimmering auroras, like the Northern Lights, that briefly dance at our planet’s poles. But, on Jupiter, there’s an auroral glow all the time, and new observations show that this Jovian display sometimes flares up because of a process having nothing to do with the Sun.

Jupiter watchers have long known that the giant planet’s ever-present polar auroras – thousands of times brighter and many times bigger than Earth – are powered by both electrically charged particles from the Sun colliding with Jupiter’s magnetic field and a separate interaction between Jupiter and one of its many moons, called Io. But there are also auroral explosions on Jupiter, or periods of dazzling brightening, similar to auroral storms on Earth, that no one could definitively trace back to either of those known causes.

In the aurora-making interaction of Jupiter and Io, volcanoes on the small moon blast clouds of electrically charged atoms (ions) and electrons into a region surrounding Jupiter that’s permeated by the planet’s powerful magnetic field, thousands of times stronger than Earth’s. Rotating along with its rapidly spinning planet, the magnetic field drags the material from Io around with it, causing strong electric fields at Jupiter’s poles. The acceleration of the ions and electrons produce intense auroras that shine in almost all parts of the electromagnetic spectrum but most brightly in high-energy bands, like ultraviolet light and X-rays, that are invisible to unaided human eyes.

Now, new observations of the planet’s extreme ultraviolet emissions show that bright explosions of Jupiter’s aurora likely also get kicked off by the planet-moon interaction, not by solar activity. A new scientific paper about these observations by Tomoki Kimura of the Japan Aerospace Exploration Agency (JAXA), in Sagamihara, Kanagawa, Japan, and his colleagues, was published online today in Geophysical Research Letters, a journal of the American Geophysical Union.

Starting in January 2014, a telescope aboard the JAXA’s Hisaki satellite, which focused on Jupiter for two months, recorded intermittent brightening of the giant planet’s aurora. The telescope detected sudden flare-ups on days when the usual flow of charged particles from the Sun, known as the solar wind, was relatively weak.

Additional space and ground-based telescopes, including the Hubble Space Telescope, also viewed Jupiter during these lulls in the solar wind. Both Hisaki and Hubble witnessed explosions of the planet’s aurora despite the solar wind’s calm, suggesting that it’s the Jupiter-Io interaction driving these explosions, not charged particles from the Sun, according to the new study. The new research does not address exactly what is happening in the Jovian magnetosphere to cause the temporary brightening of auroral explosions.

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NASA’s Opportunity Mars Rover Finishes Marathon, Clocks in at Just Over 11 Years

This illustration depicts some highlights along the route as NASA's Mars Exploration Rover Opportunity drove as far as a marathon race during the first 11 years and two months after its January 2004 landing in Eagle Crater. The vehicle surpassed marathon distance of 26.219 miles (42.195 kilometers) with a drive completed on March 24, 2015, during the 3,968th Martian day, or sol, of Opportunity's work on Mars. For this map, north is on the left. Image Credit: NASA/JPL-Caltech/Cornell Univ./USGS/Arizona State Univ.

This illustration depicts some highlights along the route as NASA’s Mars Exploration Rover Opportunity drove as far as a marathon race during the first 11 years and two months after its January 2004 landing in Eagle Crater. The vehicle surpassed marathon distance of 26.219 miles (42.195 kilometers) with a drive completed on March 24, 2015, during the 3,968th Martian day, or sol, of Opportunity’s work on Mars. For this map, north is on the left. Image Credit: NASA/JPL-Caltech/Cornell Univ./USGS/Arizona State Univ.

There was no tape draped across a finish line, but NASA is celebrating a win. The agency’s Mars Exploration Rover Opportunity completed its first Red Planet marathon Tuesday — 26.219 miles (42.195 kilometers) – with a finish time of roughly 11 years and two months.

“This is the first time any human enterprise has exceeded the distance of a marathon on the surface of another world,” said John Callas, Opportunity project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “A first time happens only once.”

This map shows the rover's entire traverse from landing to that point. Image Credit: NASA/JPL-Caltech/MSSS/NMMNHS

This map shows the rover’s entire traverse from landing to that point. Image Credit: NASA/JPL-Caltech/MSSS/NMMNHS

The rover team at JPL plans a marathon-length relay run at the laboratory next week to celebrate.

The long-lived rover surpassed the marathon mark during a drive of 153 feet (46.5 meters). Last year, Opportunity became the long-distance champion of all off-Earth vehicles when it topped the previous record set by the former Soviet Union’s Lunokhod 2 moon rover.

“This mission isn’t about setting distance records, of course; it’s about making scientific discoveries on Mars and inspiring future explorers to achieve even more,” said Steve Squyres, Opportunity principal investigator at Cornell University in Ithaca, New York. “Still, running a marathon on Mars feels pretty cool.”

Opportunity’s original three-month prime mission in 2004 yielded evidence of environments with liquid water soaking the ground and flowing on planet’s surface.

This map shows the southward path driven by Opportunity from late December 2014 until it passed marathon distance on March 24, 2015, during the 3,968th Martian day, or sol, of the rover's work on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

This map shows the southward path driven by Opportunity from late December 2014 until it passed marathon distance on March 24, 2015, during the 3,968th Martian day, or sol, of the rover’s work on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

As the rover continued to operate far beyond expectations for its lifespan, scientists chose the rim of Endeavour Crater as a long-term destination. Since 2011, examinations of Endeavour’s rim have provided information about ancient wet conditions less acidic, and more favorable for microbial life, than the environment that left clues found earlier in the mission.

JPL manages the Mars rover projects for NASA’s Science Mission Directorate in Washington. The Mars Exploration Rover Project, NASA’s newer Curiosity Mars rover, and three active NASA Mars orbiters are part of NASA’s Mars Exploration Program, which seeks to characterize and understand Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. In parallel, NASA is developing the human spaceflight capabilities needed for its journey to Mars.

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Curiosity Rover Finds Biologically Useful Nitrogen on Mars

This self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity's work on Mars (Feb. 3, 2013), plus three exposures taken during Sol 270 (May 10, 2013) to update the appearance of part of the ground beside the rover.

This self-portrait of NASA’s Mars rover Curiosity combines dozens of exposures taken by the rover’s Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity’s work on Mars (Feb. 3, 2013), plus three exposures taken during Sol 270 (May 10, 2013) to update the appearance of part of the ground beside the rover.

A team using the Sample Analysis at Mars (SAM) instrument suite aboard NASA’s Curiosity rover has made the first detection of nitrogen on the surface of Mars from release during heating of Martian sediments.

The nitrogen was detected in the form of nitric oxide, and could be released from the breakdown of nitrates during heating. Nitrates are a class of molecules that contain nitrogen in a form that can be used by living organisms. The discovery adds to the evidence that ancient Mars was habitable for life.

Nitrogen is essential for all known forms of life, since it is used in the building blocks of larger molecules like DNA and RNA, which encode the genetic instructions for life, and proteins, which are used to build structures like hair and nails, and to speed up or regulate chemical reactions.

However, on Earth and Mars, atmospheric nitrogen is locked up as nitrogen gas (N2) – two atoms of nitrogen bound together so strongly that they do not react easily with other molecules. The nitrogen atoms have to be separated or “fixed” so they can participate in the chemical reactions needed for life. On Earth, certain organisms are capable of fixing atmospheric nitrogen and this process is critical for metabolic activity. However, smaller amounts of nitrogen are also fixed by energetic events like lightning strikes.

Nitrate (NO3) – a nitrogen atom bound to three oxygen atoms – is a source of fixed nitrogen. A nitrate molecule can join with various other atoms and molecules; this class of molecules is known as nitrates.

There is no evidence to suggest that the fixed nitrogen molecules found by the team were created by life. The surface of Mars is inhospitable for known forms of life. Instead, the team thinks the nitrates are ancient, and likely came from non-biological processes like meteorite impacts and lightning in Mars’ distant past.

Features resembling dry riverbeds and the discovery of minerals that form only in the presence of liquid water suggest that Mars was more hospitable in the remote past. The Curiosity team has found evidence that other ingredients needed for life, such as liquid water and organic matter, were present on Mars at the Curiosity site in Gale Crater billions of years ago.

“Finding a biochemically accessible form of nitrogen is more support for the ancient Martian environment at Gale Crater being habitable,” said Jennifer Stern of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Stern is lead author of a paper on this research published online in the Proceedings of the National Academy of Science March 23.

The team found evidence for nitrates in scooped samples of windblown sand and dust at the “Rocknest” site, and in samples drilled from mudstone at the “John Klein” and “Cumberland” drill sites in Yellowknife Bay. Since the Rocknest sample is a combination of dust blown in from distant regions on Mars and more locally sourced materials, the nitrates are likely to be widespread across Mars, according to Stern.

The results support the equivalent of up to 1,100 parts per million nitrates in the Martian soil from the drill sites. The team thinks the mudstone at Yellowknife Bay formed from sediment deposited at the bottom of a lake. Previously the rover team described the evidence for an ancient, habitable environment there: fresh water, key chemical elements required by life, such as carbon, and potential energy sources to drive metabolism in simple organisms.

The samples were first heated to release molecules bound to the Martian soil, then portions of the gases released were diverted to the SAM instruments for analysis. Various nitrogen-bearing compounds were identified with two instruments: a mass spectrometer, which uses electric fields to identify molecules by their signature masses, and a gas chromatograph, which separates molecules based on the time they take to travel through a small glass capillary tube — certain molecules interact with the sides of the tube more readily and thus travel more slowly.

Along with other nitrogen compounds, the instruments detected nitric oxide (NO — one atom of nitrogen bound to an oxygen atom) in samples from all three sites. Since nitrate is a nitrogen atom bound to three oxygen atoms, the team thinks most of the NO likely came from nitrate which decomposed as the samples were heated for analysis.

Certain compounds in the SAM instrument can also release nitrogen as samples are heated; however, the amount of NO found is more than twice what could be produced by SAM in the most extreme and unrealistic scenario, according to Stern. This leads the team to think that nitrates really are present on Mars, and the abundance estimates reported have been adjusted to reflect this potential additional source.

“Scientists have long thought that nitrates would be produced on Mars from the energy released in meteorite impacts, and the amounts we found agree well with estimates from this process,” said Stern.

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World’s largest asteroid impacts found in central Australia

Dr Andrew Glikson with a sample of suevite - a rock with partially melted material formed during an impact. Image: D. Seymour

Dr Andrew Glikson with a sample of suevite – a rock with partially melted material formed during an impact. Image: D. Seymour

A 400 kilometre-wide impact zone from a huge meteorite that broke in two moments before it slammed into the Earth has been found in Central Australia.

The crater from the impact millions of years ago has long disappeared. But a team of geophysicists has found the twin scars of the impacts – the largest impact zone ever found on Earth – hidden deep in the earth’s crust.

Lead researcher Dr Andrew Glikson from the ANU School of Archaeology and Anthropologysaid the impact zone was discovered during drilling as part of geothermal research, in an area near the borders of South Australia, Queensland and the Northern Territory.

“The two asteroids must each have been over 10 kilometres across – it would have been curtains for many life species on the planet at the time,” said Dr Glikson.

The revelation of such ancient violent impacts may lead to new theories about the Earth’s history.

“Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought,” Dr Glikson said.

The exact date of the impacts remains unclear. The surrounding rocks are 300 to 600 million years old, but evidence of the type left by other meteorite strikes is lacking.

For example, a large meteorite strike 66 million years ago sent up a plume of ash which is found as a layer of sediment in rocks around the world. The plume is thought to have led to the extinction of a large proportion of the life on the planet, including many dinosaur species.

However, a similar layer has not been found in sediments around 300 million years old, Dr Glikson said.

“It’s a mystery – we can’t find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” he said.

A geothermal research project chanced on clues to the impacts while drilling more than two kilometres into the earth’s crust.

The drill core contained traces of rocks that had been turned to glass by the extreme temperature and pressure caused by a major impact.

Magnetic modelling of the deep crust in the area traced out bulges hidden deep in the Earth, rich in iron and magnesium, corresponding to the composition of the Earth mantle.

“There are two huge deep domes in the crust, formed by the Earth’s crust rebounding after the huge impacts, and bringing up rock from the mantle below,” Dr Glikson said.

The two impact zones total more than 400 kilometres across, in the Warburton Basin in Central Australia. They extend through the Earth’s crust, which is about 30 kilometres thick in this area.

The research has been published in journal Tectonophysics.

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Public Asked to Help Name Features on Pluto

Artist concept of Pluto and its moon Charon

Artist concept of Pluto and its moon Charon

On July 14, NASA’s New Horizons spacecraft will fly past Pluto, offering the first close-up look at that small, distant world and its largest moon, Charon.  These denizens of the outer solar system will be transformed from poorly seen, hazy bodies to tangible worlds with distinct features.

Now, the public can help decide what labels will go on the images and maps coming from the flyby.  The SETI Institute has announced the launch of its “Our Pluto” campaign, which is soliciting input on how to name features on the surfaces of Pluto and Charon.

“Pluto belongs to everyone,” says New Horizon science team member Mark Showalter, a senior research scientist at the SETI Institute.  “So we want everyone to be involved in making the map of this distant world.”

The science team will not have time to come up with names during the quick flyby, so they must assemble a library of names in advance.  Consequently, they are inviting the public to visit the web site http://ourpluto.seti.org  where they can vote for the names they think should be used to identify the most prominent features on both Pluto and Charon. They can also suggest additional names.  These must be associated with a set of broad themes related to mythology and the literature and history of exploration.

After the campaign ends on April 7, the New Horizons team will sort through the names and submit their recommendations to the International Astronomical Union (IAU). The IAU will decide how the names are used.

Currently, the best images of Pluto from the Hubble Space Telescope provide just a hint of what might be in store for the New Horizons cameras. It shows a world marked by sharp contrasts, with some areas as dark as asphalt and others as bright as snow.

Artist's concept of Pluto and its moon Charon

Artist’s concept of Pluto and its moon Charon

“The Pluto flyby this summer will be a major milestone in planetary exploration,” said Alan Stern, Principal Investigator of the New Horizons project. “We are really looking forward to hearing the public’s ideas for feature naming on Pluto and Charon.”

Showalter led the teams that used the Hubble Space Telescope to discover the two smallest known moons of Pluto, Kerberos and Styx. Those satellites were also named via a public campaign.

“The difference is that last time we only needed two names, whereas now we could need more than a hundred,” Showalter notes. “We are eager to gather recommendations from people all over the world.” The web site also includes an extremely simple ballot to allow young children to participate.

More information about the New Horizons mission:

http://www.nasa.gov/newhorizons

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Europa’s Elusive Water Plume Paints Grim Picture For Life

A graphic showing water emissions detected above Europa in Hubble Space Telescope observations from December 2012. Credit: NASA/ESA/L. Roth/SWRI/University of Cologne

A graphic showing water emissions detected above Europa in Hubble Space Telescope observations from December 2012. Credit: NASA/ESA/L. Roth/SWRI/University of Cologne

A meteorite may have been responsible for a water plume briefly spotted above Europa two years ago, implying it takes a very rare event to breach the ice on the Jovian moon.

Astrobiologists worldwide received news in December 2013 that water vapor was detected in Hubble Space Telescope observations of Jupiter’s moon Europa, which is considered one of the top potential locations in our solar system for life. Those results were published in the journal Science and led by Lorenz Roth, a planetary scientist at Texas’ Southwest Research Institute.

However, follow-up observations of Europa have revealed no plume emanating from the moon. A new paper reveals that Europa’s atmosphere is 100 times less abundant than claims in previous publications, and composed mainly of atomic rather than molecular oxygen.

Furthermore, the magnetosphere plasma, or superheated gas, at Europa’s orbit is very hot, with properties indicating that the plasma is mainly composed of ions, or charged particles, from a nearby moon called Io.

Based on the plasma properties, the rate of injection of neutral gas from the surface of Europa is very low. This means the plasma in Europa’s atmosphere has a low density, and a low escape rate into its magnetic field or magnetosphere.

Artist's conception of a plume above Europa. A plume reported emanating from the icy moon in December 2013 may be a rare phenomenon, a new study shows. Credit: NASA/ESA/K. Retherford/SWRI

Artist’s conception of a plume above Europa. A plume reported emanating from the icy moon in December 2013 may be a rare phenomenon, a new study shows. Credit: NASA/ESA/K. Retherford/SWRI

No one knew what the plasma was made of before Cassini’s measurements, which led some researchers previously to believe that the plasma came from Europa. Plasma, superheated gas, can be comprised of different molecules, including hydrogen and oxygen, but Cassini’s spectroscope was not designed to measure which species of molecules were present in the gas.

Because molecular hydrogen and atomic hydrogen were not found in Cassini’s measurement of the plasma, this means that the plasma did not come from Europa as was previously suspected. The plasma that as detected was made of sulfur dioxide – a product of volcanoes on Io.

“Our conclusion was that almost everything we were seeing was plasma from Io,” said Don Shemansky, Chief Scientist of the planetary and space science division of space weather company Space Environment Technologies (PSSD/SET).

However, a meteorite that briefly threw water aloft from Europa’s surface cannot be ruled out, he said.

The results were published in the Astrophysical Journal.

Volcanic plasma

Shemansky has spent most of his life exploring the Solar System through the eyes of various NASA spacecraft, notably including Voyager and Cassini. The lead author and coauthors are team members of the Cassini UVIS experiment. The new data comes from a five-month Cassini flyby of Jupiter in 2000 and 2001.

Scientists already knew there was plasma, or superheated gas, in the vicinity of Europa based on data from Voyager’s flyby, as well as the long-term Galileo mission, which explored Jupiter and its moons in the 1990s and 2000s. Those instruments, however, couldn’t distinguish between different elements in the plasma and, therefore, could not determine the origin of the plasma. That’s where Cassini was different.

Cassini confirmed a similar concentration of plasma that Voyager and Galileo saw. It further detected a mix of sulfur and oxygen ions that most likely come from Io. The moon’s volcanic activity spews these elements into its orbit, creating a plasma “torus” that Europa’s orbit also passes through.

“This points to very little output from Europa,” Shemansky said.

This would mean that any output that scientists see in the area is from Io, not Europa, which has grim implications for life.

Europa would need to have fissures in its surface to allow for contact between its hypothetical underground ocean and the combined effects of the magnetosphere and solar input on its surface. The energy input would include gravitational flexure by Jupiter in addition to the sun and magnetosphere. If the plume is a rare event, this means there are likely few or no cracks in the surface. Europa might be a socked-in icy ball with a barren ocean below.

A closer view of Europa's icy surface, with a potential ocean underneath. Credit: NASA/JPL-Caltech/SETI Institute

A closer view of Europa’s icy surface, with a potential ocean underneath. Credit: NASA/JPL-Caltech/SETI Institute

Shemansky emphasizes that he has no reason to doubt the Roth et. al. observations. The spectroscopy they saw, replete with atomic oxygen, was in similar quantities you would expect if water molecules were breaking apart. The water’s hydrogen has enough energy to escape into the magnetosphere (the magnetic environment around Europa), while the oxygen remains closer to the surface.

“They were presenting for the first time what you would call direct evidence that we have water,” Shemansky said.

But there were three issues with the theory, he said. While he says there is no reason to doubt the observations yet, it is the only direct indication of water ejection from the surface, the observation has not been repeated, and there was nothing unusual detected on the planet’s surface at the time of the ejection.

Data collection problems

Io as a major source of mass and subsequent accumulation of energy in the magnetosphere is a conclusion drawn in the review a decade ago by Christopher Russell, a planetary scientist at the University of California, Los Angeles who examined the role of the volcanic moon’s emissions in Jupiter’s environment. The work was based in part on Voyager and Galileo observations.

“He paints a general picture that Io is the primary producer of mass that goes into the magnetosphere,” Shemansky said.

He added that the radiation is easy to observe because there is so much energy associated with the Io torus. The energy comes from the rotation of Jupiter’s magnetic field, which whips around quickly because the gas giant rotates with a 10 hour period.

Europa’s plume reached a couple of hundred kilometers above the surface according to Roth et al, but did not have enough energy to escape into to the magnetosphere, Shemansky added.

“The plume collapsed onto the moon’s body, and that was the end.”

More observations will be needed to confirm what happened during the plume’s eruption, but Shemansky said one theory could have been that a meteorite created a fissure in the surface that subsequently healed. There could, however, be more evidence lurking in archival data.

Because there is so much data flowing from each mission, and inadequate resources to analyze it, often information is archived without the chance to look at it. It took Shemansky’s team nearly 15 years to look back at Europa’s plasma environment based on the Cassini flyby, and he said there are reams of data available from Cassini’s orbits around Saturn that may not be looked at for years or decades to come, unless more funding appears.

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International study raises questions about cause of global ice ages

A new international study casts doubt on the leading theory of what causes ice ages around the world — changes in the way the Earth orbits the sun.

Moraines, or rocks and soil deposited by glaciers during the Last Glacial Maximum, are spread across the landscape near Mt. Cook, New Zealand's tallest mountain, and Lake Pukaki. Credit: Aaron Putnam

Moraines, or rocks and soil deposited by glaciers during the Last Glacial Maximum, are spread across the landscape near Mt. Cook, New Zealand’s tallest mountain, and Lake Pukaki. Credit: Aaron Putnam

The researchers found that glacier movement in the Southern Hemisphere is influenced primarily by sea surface temperature and atmospheric carbon dioxide rather than changes in the Earth’s orbit, which are thought to drive the advance and retreat of ice sheets in the Northern Hemisphere.

The findings appear in the journal Geology. A PDF is available on request.

The study raises questions about the Milankovitch theory of climate, which says the expansion and contraction of Northern Hemisphere continental ice sheets are influenced by cyclic fluctuations in solar radiation intensity due to wobbles in the Earth’s orbit; those orbital fluctuations should have an opposite effect on Southern Hemisphere glaciers.

“Records of past climatic changes are the only reason scientists are able to predict how the world will change in the future due to warming. The more we understand about the cause of large climatic changes and how the cooling or warming signals travel around the world, the better we can predict and adapt to future changes,” says lead author Alice Doughty, a glacial geologist at Dartmouth College who studies New Zealand mountain glaciers to understand what causes large-scale global climatic change such as ice ages.

“Our results point to the importance of feedbacks — a reaction within the climate system that can amplify the initial climate change, such as cool temperatures leading to larger ice sheets, which reflect more sunlight, which cools the planet further. The more we know about the magnitude and rates of these changes and the better we can explain these connections, the more robust climate models can be in predicting future change.”

The researchers used detailed mapping and beryllium-10 surface exposure dating of ice-age moraines – or rocks deposited when glaciers move — in New Zealand’s Southern Alps, where the glaciers were much bigger in the past. The dating method measures beryllium-10, a nuclide produced in rocks when they are struck by cosmic rays.

The researchers identified at least seven episodes of maximum glacier expansion during the last ice age, and they also dated the ages of four sequential moraine ridges. The results showed that New Zealand glaciers were large at the same time that large ice sheets covered Scandinavia and Canada during the last ice age about 20,000 years ago.

This makes sense in that the whole world was cold at the same time, but the Milankovitch theory should have opposite effects for the Northern and Southern Hemispheres, and thus cannot explain the synchronous advance of glaciers around the globe. Previous studies have shown that Chilean glaciers in the southern Andes also have been large at the same time as Northern Hemisphere ice sheets.

The ages of the four New Zealand ridges – about 35,500; 27,170; 20,270; and 18,290 years old — instead align with times of cooler sea surface temperatures off the coast of New Zealand based on offshore marine sediment cores. The timing of the Northern Hemisphere’s ice ages and large ice sheets is still paced by how Earth orbits the Sun, but how the cooling and warming signals are transferred around the world has not been fully explained, although ocean currents (flow direction, speed and temperature) play a significant role.

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2015 Arctic Sea Ice Maximum Annual Extent Is Lowest On Record

The sea ice cap of the Arctic appeared to reach its annual maximum winter extent on Feb. 25, according to data from the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder. At 5.61 million square miles (14.54 million square kilometers), this year’s maximum extent was the smallest on the satellite record and also one of the earliest.

Arctic sea ice likely reached its annual maximum winter extent on Feb. 25, barring a late season surge. At 5.61 million square miles (14.54 million square kilometers), this year's winter peak extent is the lowest and one of the earliest on the satellite record that began in 1979. Image Credit: NASA's Goddard Space Flight Center

Arctic sea ice likely reached its annual maximum winter extent on Feb. 25, barring a late season surge. At 5.61 million square miles (14.54 million square kilometers), this year’s winter peak extent is the lowest and one of the earliest on the satellite record that began in 1979. Image Credit: NASA’s Goddard Space Flight Center

Arctic sea ice, frozen seawater floating on top of the Arctic Ocean and its neighboring seas, is in constant change: it grows in the fall and winter, reaching its annual maximum between late February and early April, and then it shrinks in the spring and summer until it hits its annual minimum extent in September. The past decades have seen a downward trend in Arctic sea ice extent during both the growing and melting season, though the decline is steeper in the latter.

This year’s maximum was reached 15 days earlier than the 1981 to 2010 average date of March 12, according to NSIDC. Only in 1996 did it occur earlier, on Feb. 24. However, the sun is just beginning to rise on the Arctic Ocean and a late spurt of ice growth is still possible, though unlikely.

This short video shows the bulk of the Arctic sea ice freeze cycle from October through this year’s apparent winter maximum on Feb. 25. Image Credit: NASA’s Goddard Space Flight Center/J. Beck

If the maximum were to remain at 5.61 million square miles, it would be about 50,000 square miles below the previous lowest peak wintertime extent, reached in 2011 at 5.66 million square miles — in percentages, that’s less than a 1 percent difference between the two record low maximums. In comparison, the swings between record lows for the Arctic summertime minimum extent have been much wider: the lowest minimum extent on record, in 2012, was 1.31 million square miles, about 300,000 square miles, or 18.6 percent smaller than the previous record low one, which happened in 2007 and clocked at 1.61 million square miles.

A record low sea ice maximum extent does not necessarily lead to a record low summertime minimum extent.

“The winter maximum gives you a head start, but the minimum is so much more dependent on what happens in the summer that it seems to wash out anything that happens in the winter,” said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“If the summer is cool, the melt rate will slow down. And the opposite is true, too: even if you start from a fairly high point, warm summer conditions make ice melt fast. This was highlighted by 2012, when we had one of the later maximums on record and extent was near-normal early in the melt season, but still the 2012 minimum was by far the lowest minimum we’ve seen.”

Here the 2015 maximum is compared to the 1979-2014 average maximum shown in yellow. A distance indicator shows the difference between the two in the Sea of Okhotsk north of Japan. Image Credit: NASA's Goddard Space Flight Center

Here the 2015 maximum is compared to the 1979-2014 average maximum shown in yellow. A distance indicator shows the difference between the two in the Sea of Okhotsk north of Japan. Image Credit: NASA’s Goddard Space Flight Center

The main player in the wintertime maximum extent is the seasonal ice at the edges of the ice pack. This type of ice is thin and at the mercy of which direction the wind blows: warm winds from the south compact the ice northward and also bring heat that makes the ice melt, while cold winds from the north allow more sea ice to form and spread the ice edge southward.

“Scientifically, the yearly maximum extent is not as interesting as the minimum. It is highly influenced by weather and we’re looking at the loss of thin, seasonal ice that is going to melt anyway in the summer and won’t become part of the permanent ice cover,” Meier said. “With the summertime minimum, when the extent decreases it’s because we’re losing the thick ice component, and that is a better indicator of warming temperatures.”

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Search for extraterrestrial intelligence extends to new realms

New instrument will scan the sky for pulses of infrared light

Astronomers have expanded the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light. Their new instrument has just begun to scour the sky for messages from other worlds.

The NIROSETI team with their new infrared detector inside the dome at Lick Observatory. Left to right: Remington Stone, Dan Wertheimer, Jérome Maire, Shelley Wright, Patrick Dorval and Richard Treffers. Photos by © Laurie Hatch

The NIROSETI team with their new infrared detector inside the dome at Lick Observatory. Left to right: Remington Stone, Dan Wertheimer, Jérome Maire, Shelley Wright, Patrick Dorval and Richard Treffers. Photos by © Laurie Hatch

“Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an Assistant Professor of Physics at the University of California, San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

Pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from greater distances. It also takes less energy to send the same amount of information using infrared signals than it would with visible light.

The idea dates back decades, Wright pointed out. Charles Townes, the late UC Berkeley scientist whose contributions to the development of lasers led to a Nobel Prize, suggested the idea in a paper published in 1961.

Scientists have searched the heavens for radio signals for more than 50 years and expanded their search to the optical realm more than a decade ago. But instruments capable of capturing pulses of infrared light have only recently become available.

Shelley Wright holds a fiber tht emits infrared light for calibration of the detectors

Shelley Wright holds a fiber tht emits infrared light for calibration of the detectors

“We had to wait,” Wright said, for technology to catch up. “I spent eight years waiting and watching as new technology emerged.”

Three years ago while at the Dunlap Institute, Wright purchased newly available detectors and tested them to see if they worked well enough to deploy to a telescope. She found that they did. Jérome Maire, a Fellow at the Dunlap, “turned the screws,” Wright said, playing a key role in the hands-on effort to develop the new instrument, called NIROSETI for near-infrared optical SETI.

NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed to for potential signs of other civilizations, a record that could be revisited as new ideas about what signals extraterrestrials might send emerge.

Because infrared light penetrates farther through gas and dust than visible light, this new search will extend to stars thousands rather than merely hundreds of light years away. And the success of the Kepler Mission, which has found habitable planets orbiting stars both like and unlike our own, has prompted the new search to look for signals from a wider variety of stars.

NIROSETI has been installed at the University of California’s Lick Observatory on Mt. Hamilton east of San Jose and saw first light on March 15.

Skies cleared for a successful first night for NIROSETI at Lick Observatory. The ghost image is Shelley Wright, pausing for a moment during this long exposure as the rest of her team continued to test the new instrument inside the dome.

Skies cleared for a successful first night for NIROSETI at Lick Observatory. The ghost image is Shelley Wright, pausing for a moment during this long exposure as the rest of her team continued to test the new instrument inside the dome.

Lick Observatory has been the site of several previous SETI searches including an instrument to look in the optical realm, which Wright built as an undergraduate student at UC Santa Cruz under the direction of Remington Stone, the director of operations at Lick at that time. Dan Werthimer and Richard Treffers of UC Berkeley designed that first optical instrument. All three are playing critical roles in the new search.

NIROSETI could uncover new information about the physical universe as well. “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” Werthimer said. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

Patrick Dorval, Jérome Maire and Shelley Wright in the control room of the Nickel 1-meter telescope at Lick Observatory, where their new instrument has been deployed.

Patrick Dorval, Jérome Maire and Shelley Wright in the control room of the Nickel 1-meter telescope at Lick Observatory, where their new instrument has been deployed.

The group also includes SETI pioneer Frank Drake of the SETI Institute and UC Santa Cruz who serves as a senior advisor to both past and future projects and is an active observer at the telescope.

Drake pointed out several additional advantages to a search in this new realm. “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success.” he said. The receivers are also much more affordable that those used on radio telescopes.

“There is only one downside: the extraterrestrials would need to be transmitting their signals in our direction,” Drake said, though he sees a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student. Shelley Wright is also a member of the Center for Astrophysics and Space Sciences at UC San Diego. Richard Treffers is now at Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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Iron rain fell on early Earth, new Z machine data supports

An artist’s concept shows a celestial body about the size of our moon slamming at great speed into a body the size of Mercury. (Image courtesy of NASA/JPL-Caltech)

An artist’s concept shows a celestial body about the size of our moon slamming at great speed into a body the size of Mercury. (Image courtesy of NASA/JPL-Caltech)

Researchers at Sandia National Laboratories’ Z machine have helped untangle a long-standing mystery of astrophysics: why iron is found spattered throughout Earth’s mantle, the roughly 2,000-mile thick region between Earth’s core and its crust.

At first blush, it seemed more reasonable that iron arriving from collisions between Earth and  planetesimals — ranging from several meters to hundreds of kilometers in diameter — during Earth’s late formative stages should have powered bullet-like directly to Earth’s core, where so much iron already exists.

A second, correlative mystery is why the moon proportionately has much less iron in its mantle than does Earth. Since the moon would have undergone the same extraterrestrial bombardment as its larger neighbor, what could explain the relative absence of that element in the moon’s own mantle?

To answer these questions, scientists led by Professor Stein Jacobsen at Harvard University and Professor Sarah Stewart at the University of California at Davis (UC Davis) wondered whether the accepted theoretical value of the vaporization point of iron under high pressures was correct. If vaporization occurred at lower pressures than assumed, a solid piece of iron after impact might disperse into an iron vapor that would blanket the forming Earth instead of punching through it. A resultant iron-rich rain would create the pockets of the element currently found in the mantle.

As for the moon, the same dissolution of iron into vapor could occur, but the satellite’s weaker gravity would be unable to capture the bulk of the free-floating iron atoms, explaining the dearth of iron deposits on Earth’s nearest neighbor.

Looking for experimental rather than theoretical values, researchers turned to Sandia’s Z machine and its Fundamental Science Program, coordinated by Sandia manager Thomas Mattsson. This led to a collaboration among Sandia, Harvard University, UC Davis, and Lawrence Livermore National Laboratory (LLNL) to determine an experimental value for the vaporization threshold of iron that would replace the theoretical value used for decades.

Sandia National Laboratories Z machine is the most powerful producer of pulses of electrical energy on Earth. (Photo by Randy Montoya)

Sandia National Laboratories Z machine is the most powerful producer of pulses of electrical energy on Earth. (Photo by Randy Montoya)

Rick Kraus at LLNL (formerly at Harvard) and Sandia researchers Ray Lemke and Seth Root used Z to accelerate metals to extreme speeds using high magnetic fields. The researchers created a target that consisted of an iron plate 5 millimeters square and 200 microns thick, against which they launched aluminum flyer plates travelling up to 25 kilometers per second. At this impact pressure, the powerful shock waves created in the iron cause it to compress, heat up and — in the zero pressure resulting from waves reflecting from the iron’s far surface — vaporize.

The result, published March 2 in Nature Geosciences under the title “Impact vaporization of planetesimal cores in the late stages of planet formation,” shows the shock pressure experimentally required to vaporize iron is approximately 507 gigapascals (GPa), undercutting by more than 40 percent the previous theoretical estimate of 887 GPa. Astrophysicists say that this lower pressure is readily achieved during the end stages of planetary growth through accretion.

Principal investigator Kraus said, “Because planetary scientists always thought it was difficult to vaporize iron, they never thought of vaporization as an important process during the formation of the Earth and its core. But with our experiments, we showed that it’s very easy to impact-vaporize iron.”

He continued, “This changes the way we think of planet formation, in that instead of core formation occurring by iron sinking down to the growing Earth’s core in large blobs (technically called diapirs), that iron was vaporized, spread out in a plume over the surface of the Earth and rained out as small droplets. The small iron droplets mixed easily with the mantle, which changes our interpretation of the geochemical data we use to date the timing of Earth’s core formation.”