On the Other Neighbor, Follow the Lava
Mars may be beckoning to earthlings today, but our other planetary neighbor, Venus, is seductive-- at least to those seeking exotic places to visit.
Both photo-historians and futurists may be rewarded by looking to Venus. When one photo-historian of the 1970's Venusian landers, Don Mitchell, viewed the high-resolution Mars panoramas, he was motivated to revisit some of the most remarkable Soviet landers to that other neighboring planet, Venus. The banner image (click to enlarge) reveals just one example from the Venera photolog and showcases what some kinds of modern processing steps might deliver tomorrow for Venusian surface landers.
Mitchell wrote: "Since the [Venera] scene was scanned several times, it may be possible to calculate a super-resolution image from multiple panoramas, as NASA has done with Mars Pathfinder images." Mitchell told Astrobiology Magazine that his "primary mission, to work on the Venera-13 data, is not finished yet", but the online version gives a remarkable glimpse into one of the least understood planetary surfaces in our solar system.
" My involvement directly in the space program was in the late 1970s", said Mitchell, "when I worked on the [cosmic ray, or Heavy Nuclei experiments, with the] HEAO-C satellite at Caltech. I've primarily worked on computer graphics, as a researcher at AT&T Bell Labs, Princeton and Microsoft. So I've gone from space science to computer science."
The history of Venera is interlocked with the memories of cold-war politics and planetary milestones. Rather than duplicating NASA efforts, the [Soviet space] leadership made a controversial decision to abandon immediate plans for Mars exploration and jump-start a series of missions to Venus, known in the USSR as "Venera." "We had to work in a different 'weight category': Venera-type missions were worth 100 million rubles versus the $800 million Viking," then Director, Roald Sagdeev, wrote in his memoirs. From the engineering standpoint, Venus could be reached faster than Mars -- an important factor for the Soviet scientists, facing serious challenges with the reliability of avionics onboard the spacecraft. Additionally, the same launch vehicle would be able to send heavier payload toward Venus than to Mars, therefore allowing bigger spacecraft with more redundancy built in.
The Venera series provided remarkably clear pictures from an otherwise cloudy planet. Venera 9 landed on October 22, 1975 and captured a panoramic view before its signal terminated. Later missions in the Venera series also transmitted panoramic views. The size of most Venusian rocks in the images was estimated to be around 50-70 centimeters and the height 15-20 centimeters. Most rocks featured sharp edges, hinting either their geologically young age, or very slow process of erosion. The current series of Mars rovers are seeking landing sites that have less than eight percent rock coverage to speed up their longer distance driving, but watermelon-sized rocks have been imaged in previous landing missions on the red planet.
David Grinspoon shares some of Mitchell's intrigue with revisiting exploration themes with Venus in mind. Grinspoon is a planetary scientist at the Southwest Research Institute in Boulder Colorado, Principal Investigator for NASA's Exobiology Research Program and author "Venus Revealed" and "Lonely Planets", where he describes the key questions a new prototype Venus mission might try to answer: "How soon and in what style will we go back to Venus?..We could put a small craft with a few carefully chosen instruments in orbit around Venus, or land a very small package on the surface for a ballpark figure of $200 million...here are some questions for future missions:
- What drives the superrotation of the upper atmosphere?
- What is stabilizing the climate?
- What is the 'snow' at high altitudes?
- What is the present rate of volcanic eruptions?
- What does the surface look like up close?
The Soviet Vega mission of 1985 pioneered the use of balloon stations in the Venusian atmosphere. We could do alot more along these lines. By setting balloons adrift in the atmosphere, we could learn about circulation patterns...At lower altitudes, cameras on balloons could photograph the surface as they circled the planet, getting a free ride from the superrotation. ...[For instrumentation], the two that most excite me are cameras and seismometers...there are surely places of fantastic beauty and complexity..."
|Mars (left), Earth (middle), Venus (right) with relative sizes.
Grinspoon recently told Astrobiology Magazine that the mission themes to 'follow the water' on Mars are different compared to how one might begin to explore about Venus: "The astrobiology movement is still new, but it represents a fundamental re-alignment of NASA's focus, making our scientific approach toward the universe more "biocentric." I welcome this, because the question of how life and consciousness emerged from the physical universe, and how unique these processes are to Earth, is the most exciting, fundamental, and widely accessible way to encapsulate the motivation behind so much of what NASA does...while Venus may seem a less obvious target of 'biocentric' exploration, NASA recently has included Venus on a short-list of highest priority near-future exploration goals. Venus can provide context for understanding Earth and its path to life that we can find nowhere else. (I also think that there could be life in the Venusian clouds , but that's another story)."
|Venus up-close, as photographed by the Soviet Venera 13 lander, which parachuted to the Venusian surface on March 1, 1982
As Grinspoon describes this cloudy world: "Brighter than any star, never in the same place for long, Venus is a live-wire, sparkling and dancing through our evening and morning skies."
While Venus shares with Earth a similar size (95%) and mass (80%), its thick greenhouse atmosphere has transformed a potential terrestrial twin into a hostile, burning acidic world. When the Soviet Venera landers (1975-1982) first touched down amidst solidified lava flows and acid rain, the bright planet's shroud was momentarily lifted: pictures revealed the 'morning-' and 'evening-star' up close, as if under one's feet.
In total, more than 20 spacecraft have now tried to visit Venus, most recently highlighted by the US Magellan mission to plot detailed radar maps. Unlike earlier portrayals in mythology or in science-fiction, Venus offers life-as-we-know-it a rather inhospitable place. Underneath those luminous clouds that reflect back 80% of incoming sunlight, "the most important single quality distinguishing Venus from Earth", writes Grinspoon, "is the near total lack of water there."
At least on the surface, what themes are explored on Mars as 'follow the water' get translated to Venus, as 'follow the lava'.
|Much of the surface of Venus is covered by lava flows (shown above).
The details are foreboding. At its surface, the Venusian atmosphere is 90 times denser than Earth's, or about the same as being 1 km (0.6 miles) beneath terrestrial oceans. The average surface temperature (470 degrees C, or 870 F) is hot enough to melt lead. At night, amidst distant lightning strikes high in the clouds, the ground would glow a faint red. Venus' surface is the hottest in our solar system, despite being twice the distance of Mercury from the Sun. Or as Dr. Grinspoon illustrates: "You could fry an egg on the sidewalk, but you'd have to do it quickly, before the sidewalk melted."
Venus has no tilted axis, and thus no winter, summer, nor any seasonal change. A relatively gentle breeze of a few miles per hour at the surface builds to a cloud-top gale that swirls like perpetual hurricanes: 350 km/hr, or 210 mph. While rather quiet geologically for the last few hundred million years, today's Venus is still volcanically active. Its terrain is marked by several large shield volcanoes, and is covered with solidified lava flows. Because of its slow rotation, the Venusian day and night each last 59 Earth days, or about two Earth months.
"The portrait of Venus, as a verdant, rainy, overgrown swamp planet--perhaps complete with tree ferns and jungle animals--", writes Dr. Grinspoon, "became widespread in the popular and scientific literature through the nineteenth and most of the twentieth centuries." When one considers that as recently as 1955 -just a few years before the dawn of the space-age, the famous British astrophysicist, Fred Hoyle, considered Venus to be covered planetwide in oil, apparently our nearest neighbor still has many secrets left to reveal. [Hoyle speculated upon what became known as 'Hoyle Oil': "Venus is probably endowed beyond the dreams of the richest Texas oil-king".]
In an attempt to provide some speculative context, Grinspoon has engaged the biocentricity of Venus in his book, Venus Revealed, "Admittedly, this is a long shot, but I consider life on Venus to still be an open question. In any case, thinking about it is a worthwhile exercise that may help us to better understand the real limits of life.
Reader's Advisory: This Box Contains Explict Speculation!
I have now crawled so far out on a limb that I see no reason to try climbing back. I may as well jump! So let me propose some possible signs of life on Venus. Let me state clearly that I regard each of these possibilities as extremely unlikely.
Here are four phenomena that could be signs of life on Venus:
1) The atmospheric 'superrotation' could be created by life.
This is one of the most obvious and large scale unexplained features of the planet. ..From the point of view of any Venusian bugs that want to use sunlight for energy, the superrotation would be a major plus because the night [59 days] is so long there. The planet may rotate too slowly for photosynthesis unless you have something like superrotation.
2) Maybe the 'unknown ultraviolet absorber' is a photosynthetic pigment.
|Ultraviolet image of Venus obtained by Pioneer-12.
Image Credit: BNSC
If Venusian life has evolved to take advantage of UV light, this might be done in the form of a pigment that absorbs ultraviolet. If this is some complex chemical unknown to us, that could explain why we have had such a tough time figuring out the identity of the 'unknown ultraviolet absorber'. [Venus viewed with an ultraviolet filter shows] a complex swirl of high contrast features, ranging from finely, detailed splotches to huge planetwide streaks. And the stuff moves around like crazy. The identity of this material, so dark in the ultraviolet that it is responsible for nearly half of the solar energy absorbed by Venus, is still not known, one of the great mysteries of Venus.
3) Maybe Mode 3 cloud particles are alive.
Mode 3 are the odd, large cloud particles. ...we do not have a good description of them or explanation for them. Some measurements suggest that they are made of sulfuric acid...but there is also evidence of more exotic chemicals, like chlorine or nitrogen compounds...In fact, conditions in the clouds of Venus are not too different from those at the surface of the Earth. There is a level in the clouds (about 33 miles up), where the atmospheric pressure is about 70% of the pressure at sea level on Earth, and the temperature is a balmy 107 degrees Fahrenheit. ..It's cool enough for liquid water, and small amounts of it exist there (in a strong sulfuric acid solution). Still, something in my gut tells me that the clouds of Venus are not a good biological habitat. That something is stomach acid, hydrochloric acid. Acid eats organic molecules.
4) The highly reflective mountain tops could be covered with life.
Some kind of transformation happens to the ground all around the planet above an altitude of 13,000 feet (which corresponds to a temperature of 820 degrees).
Now that I have gotten those flights of fantasy out of my system, it's time to come back down to Earth--or at least to Venus. Here is another reason why the possibilities of life on Venus may not be completely academic to students of exobiology: there are probably more Venus-like than Earth-like planets in the universe.
We know, for sure, that there are signs of life at a few places on Venus. We know because we left them there--the smashed, corroding remains of our inquisitive machines. The most recent addition to this smattering of Earth-junk is whatever is left of Magellan".
Related Web Pages
Soviet Exploration of Venus
Dr. David Grinspoon's FunkyScience.net
Magellan Image Server
Magellan Mission Home
Fact Sheet on Venus
Past Missions to Venus
Atmosphere and Weather on Venus
Chemical Weathering Reactions on Venus