By Cheryl Pellerin
USINFO Staff Writer

This is the second article in a two-part series on the international exploration of Mars.

Washington – Space exploration might have begun as a competition among nations, but in the 21st century it is an international enterprise, with scientists from many countries participating in each mission.

Today, Mars is the focus of four missions with international participation – NASA’s Mars Odyssey (launched in 2001), the European Space Agency’s (ESA) Mars Express (2003), NASA’s Mars exploration rovers (2003) and NASA’s Mars Reconnaissance Orbiter (2005). The missions are designed to study everything from planetary geology, mineral composition, water supply, radiation and atmosphere, to whether the Red Planet can support life. (See related article.)

“For both NASA and ESA,” said David Beaty, chief scientist for the Mars Program at NASA’s Jet Propulsion Laboratory (JPL) in California, in a March 20 USINFO interview, “the mission concept is developed and put out for competition. The philosophy on both sides of the Atlantic is that the best ideas deserve to be on the mission, whether the best ideas come from U.S. scientists or Canadian scientists or European scientists.”

As to what scientists have learned so far about the Red Planet, many answers will have to wait until July, for the Seventh International Conference on Mars, to be held in California.

“For us, Beaty said, “that conference, which happens once every four years, is like the Olympics of Mars conferences. That’s the time when we get the community together to reflect on the questions – what do we agree on and what is still under debate.”

THE FUTURE ON MARS

The next mission to Mars begins this year, with more following in 2009, 2011 and 2013.

Scheduled for launch in August 2007, NASA’s Phoenix mission will study the history of water and habitability potential in the Martian arctic's ice-rich soil. Partners in the mission will come from NASA, academia and industry, and include contributions from Switzerland, Germany and Canada. Phoenix was so named because, like the mythical bird, it is rising from the remains of a predecessor – a 2001 Mars lander that never was flown.

Mars Science Laboratory, scheduled for a 2009 launch, builds on the success of rover geologists Spirit and Opportunity that arrived at Mars in 2004. NASA's next rover mission will collect Martian soil samples and rock cores and analyze them for organic compounds and environmental conditions that could have supported microbial life now or in the past. International contributors include Russia, Spain and Canada.

Mars Scout, expected to launch in 2011, is part of NASA’s Scout program, an initiative to solicit bids for smaller, lower-cost spacecraft. This Mars mission is the first mission in this program. Proposals come from the science community, according to NASA, and could involve airborne vehicles (airplanes or balloons) or small landers as investigation platforms.

ESA’s ExoMars rover, expected to launch in 2013, will further characterize the biological environment on Mars in preparation for robotic missions and later human exploration. Data from the mission are expected to provide input for broader studies of exobiology – the search for life on other planets.

LOOKING FOR LIFE ON MARS

ESA chose a NASA tool – called Urey: Mars Organic and Oxidant Detector – as part of the science payload for ExoMars. The rover will grind samples of Martian soil to fine powder and deliver them to a suite of analytical instruments, including Urey, that will search for signs of life.

Urey, named after American Nobel Prize winning chemist Harold Urey, can detect several types of organic molecules, such as amino acids that are the basis of life on Earth, at concentrations as low as a few parts per trillion.

All Earth life assembles chains of amino acids to make proteins. But amino acids do not have to originate from living organisms – it is possible that Mars has amino acids but never has had life. Most amino acids exist in left-handed and right-handed forms whose molecules mirror each other, as with the human left and right hands. Amino acids from nonbiological sources occur on a fairly even mix of right-handed and left-handed forms.

Almost all life on Earth, from the simplest microbes to the largest plants and animals, makes and uses only left-handed amino acids. Uniformity – all left or all right – is expected in any extraterrestrial life that uses mirror-image building blocks because a mixture would complicate biochemistry.

"The Urey instrument will be able to distinguish between left-handed amino acids and right-handed ones," said Allen Farrington, Urey project manager at JPL, which will build the instrument to be sent to Mars.

If Urey finds an even mix of mirror-image molecules on Mars, that could suggest Earth-like life never began on Mars. All left or all right would be strong evidence that life currently exists there, with all-right amino acids implying an origin separate from Earth life. Discovery of an uneven distribution between left and right would suggest that Martian life once existed, because amino acids created biologically gradually change toward an even mixture in the absence of life.

See also “Mechanized Explorers Studdy the Depths, Chemistry of Mars.”

More information about the Mars Exploration Program is available on NASA’s Web More information about the MarsExpress is available on the ESA Web site.

For additional information on U.S. support for space exploration, see Science and Technology.