Venus: Sizing Up the Solar System

UV_venus
Ultraviolet image of Venus obtained by Pioneer-12.
Image Credit: BNSC

Six years ago, then NASA Associate Administrator Wesley Huntress, Jr., stated , "Wherever liquid water and chemical energy are found, there is life. There is no exception." Few opportune years like 2004 have presented astrobiology with as many remarkable vistas and fresh perspectives on this fundamental triad of water, chemical energy and life.

Consider this year’s accomplishments of those dedicated to searching for life in the universe.

Landing on Mars not once, but twice. Then finding evidence for water on opposite sides of the red planet. Picking up what appears to be methane signals in the martian atmosphere, one of the residues that might prove one day to be the product of underground biology. Scientists began to discuss seriously what colonization strategies make sense.

Setting off to explore the even richer atmosphere of the Earth-like moon, Titan. Spiraling into orbital capture around Saturn and photographing its majestic rings.

Flying through the tail of a comet and heading home after collecting the first extraterrestrial samples from such dusty iceballs. Launching the Deep Impact probe to smash into a comet and watch how the dust and ice get kicked up.

Filling the astronomy catalogs with well over a hundred new planets, including what may prove to be the first visible exoplanet. Finding some nearby candidates that might occupy temperate locations or safely orbit Sun-like stars.

Witnessing the once-per-century passage of our neighboring Venus across the face of the Sun. The MESSENGER probe took off on its decade long tour of the inner solar system to orbit Mercury.

Discovering the largest planetoids beyond Pluto among those outer nurseries where only comets visit.

The editors of Astrobiology Magazine revisit the highlights of the year and where possible point to one of the strongest lineups ever for beginning a new turn of the calendar. Between the marathon still being run by the twin Mars rovers and the expected descent to Saturn’s moon, Titan, next year promises no letdowns.

transit_venus
Venus Transiting the Sun, June 8, as seen by TRACE Image Credit: NASA/TRACE

Number nine on the countdown of 2004 highlights was the June 8th eclipse of the Sun by Venus. A Venus transit occurs when, from an earthly perspective, Venus crosses in front of the sun. When it happens, once every 122 years, there are two transits eight years apart. The next crossing happens in 2012 and will be visible to people on the U.S. West Coast.

The Venus transit was a global event. The eclipse was visible from approximately 75 percent of the Earth. Only the two inner planets, Mercury and Venus, can show this phenomenon, but the last time a transit happened involving Venus was in 1882, thus making the event the rarest of eclipses.

Astronomers once used the last Venus transit to discover the distances between the sun and all the planets of the solar system. One could imagine a popular curiousity for the science community to know the scale of our solar system.

Using other methods today, the solar system is known to centimeter scales or better in accuracy. However, observing the transit of Venus still plays an important role in astronomy today. Those who search for extrasolar planets can use the same observational methods to find terrestrial planets in other star systems where hot, gaseous, Jupiter-like planets have been found. A new planet is found when the parent star’s brightness flickers or dims in a regular orbital timing.

What Next?

2005
- Mars Reconnaissance Orbiter (MRO) launch, Mars Orbiter to collect high-resolution, 1-meter, images in stereo-view of Mars
- European Venus Express, Venus Orbiter for two-year nominal mapping life [486 days, two Venus year]

2006
- New Horizons, Pluto and moon Charon flyby, mapping to outer solar system cometary fields and Kuiper Belt
- Dawn, Asteroid Ceres and Vesta rendezvous and orbiter, including investigations of asteroid water and influence on meteors
- Kepler, Extrasolar Terrestrial Planet Detection Mission, designed to look for transiting or earth-size planets that eclipse their parent stars [survey 100,000 stars]
- Europa Orbiter, planned Orbiter of Jupiters ice-covered moon, Europa, uses a radar sounder to bounce radio waves through the ice
- Japanese SELENE Lunar Orbiter and Lander, to probe the origin and evolution of the moon

2007
- Japanese Planet-C Venus Orbiter, to study the Venusian atmosphere, lightning, and volcanoes.
- Mars Scout mission, final selections August 2003 from four Scouts: SCIM, ARES, MARVEL and Phoenix
- French Mars Remote Sensing Orbiter and four small Netlanders, linked by Italian communications orbiter

2009
- BepiColumbo, European Mercury Orbiters and Lander, including Japanese collaborators, lander to operate for one week on surface
- Mars 2009, proposed long-range rover to demonstrate hazard avoidance and accurate landing dynamics


Related Web Pages

2003: Year in Review
Solar System Exploration Survey
Stardust
Genesis
Mars Opportunity Rover
Mars Spirit Rover
Mars Express
Mars Methane
New Planets
Saturn Cassini
Venus Occultation
Planet Ten: Beyond Pluto?