Cash-Poor Astrobiologists Hope for Gold in Human Exploration
Aviation Week & Space Technology, 04/10/2006, page 48
Frank Morring, Jr., Washington
Cash-poor astrobiologists hope for gold in human exploration
Astrobiologists stung by cuts in NASA's science budget hope to find common cause with well-funded human space explorers as they hunt the heavens for signs of extraterrestrial life.
U.S. astronauts are already joining their academic counterparts as they explore extreme environments on Earth for evidence of life's adaptability that can guide exploration on Mars and elsewhere. The astronauts go along for the training, primarily, although some of the sensors and equipment astrobiologists are developing for terrestrial work may find its way into space, too.
Supporters of a collaborative approach believe that ultimately the search for life, its fossil remnants and clues to its formation and evolution will be a big driver for NASA's human and robotic exploration efforts. They expect it to give both kinds of explorers a profoundly worthy objective that is already spurring agency managers to reconsider their funding balances.
Although scientists at the annual Astrobiology Science Conference (AbSciCon 2006) here last month heard hints that NASA will restore some of the 50% cut in astrobiology funds reflected in the agency's Fiscal 2007 budget request, they will only come if the scientific community at large can agree to take cuts elsewhere (AW&ST Apr. 3, p. 34).
The final decision will rest with Administrator Michael Griffin, and he says he would "on a personal basis have trouble prioritizing astrobiology at the same level as some of the other [disciplines] that I consider more important." But astrobiology also will have its champions within NASA management, and they are starting to see the benefit of working with the human-exploration mission.
"It's our commitment to assist astrobiology to the next stage, to assist the program through what we call budgetary minefields and into an alignment with the Vision for Space Exploration, because that's where the money flow's starting to go," says Marvin (Chris) Christensen, acting director of NASA's Ames Research Center, which co-sponsored AbSciCon 2006.
The change is coming just as the astrobiologists' esoteric discipline is starting to produce results. The Mars Exploration Rovers and the fleet of orbiters above them have narrowed the focus for a future search for fossil -- and perhaps even current -- life on the Red Planet. On Saturn's moon Enceladus, the Cassini probe has spotted what is believed to be another liquid-water environment. And scientists and engineers already are plotting a return to Jupiter's moon Europa, after the Galileo probe returned evidence of liquid water there.
Before they dip their instruments in the waters of Mars, Europa and Enceladus, astrobiologists are exploring the deep-ocean thermal vents and polar regions on Earth to learn more about extremophiles -- life that thrives in environments that would kill most surface-dwellers. Nathalie A. Cabrol, a geologist at NASA Ames and the SETI Institute, has studied life in the isolated lakes of the high Andes, where conditions may mimic those on Mars 3.7 billion years ago.
AT THAT TIME, a wet Mars was drying up, speculate Cabrol and her colleagues looking at the latest evidence from the Mars Exploration Rovers (MERs) and the U.S. and European Mars orbiters. The ocean that is believed to have covered the northern hemisphere of Mars might have left lakes behind as it vanished. Based on the lifeforms and other evidence in Bolivian lakes 15,000-20,000 ft. above sea level, those lakes could have sustained life from that ocean, even as conditions in them changed dramatically.
Scott Parazynski, a medical doctor and NASA astronaut with four trips to orbit under his belt, has joined Cabrol on diving expeditions in lakes on the Licancabur volcano between Chile and Bolivia. Although Parazynski's medical training was a benefit to the terrestrial explorers, he asked to participate to gain experience that NASA's Astronaut Office can apply to future missions to the Moon and Mars.
"There [is] no sound exploration without astrobiology, because we are saying where to go to explore, what to explore and [whether it is] safe to explore," says Cabrol, who has also used an experimental autonomous rover to find evidence of life in Chile's Atacama Desert. "We are also supporting human exploration by helping those guys to get the skill necessary to have safe expeditions on other worlds."
Cabrol pushed for selection of the Gusev Crater on Mars as one MER landing site, based on the terrain morphology visible from orbit. Once there, the rover Spirit was actually able to drive across the boundary between long-term dry land and rocks in the Columbia Hills that, it found, had been altered by the action of water (AW&ST Nov. 1, 2004, p. 28).
Using mobility of that sort to look for evidence of life will not be limited to places where there is liquid water, however. Astrobiologists are also interested in what the Moon can tell about the cosmic events that shaped life on Earth. Earth's inactive satellite has been a virtual data recorder for the past 2 billion years, and holds clues to events dating back to its formation 4.5 billion years ago. The geologic record on Earth, by comparison, is all but erased by the actions of water and wind.
During the AbSciCon 2006 discussions, one questioner suggested that future lunar explorers use astrobiology sensors to gauge how they are contaminating the pristine lunar environment, and then use the information to prevent a repeat at Mars that could confuse the search for life there. For Scott Hubbard, the former Ames director who holds the Sagan Chair for the Study of Life in the Universe at the SETI Institute, there is an opportunity to meld robotic and human exploration by merging the science that goes into both. He suggests setting up a "NASA Exploration Sciences Institute" that would support human and robotic exploration in astrobiology and other scientific disciplines.
While NASA is focusing its exploration funds on getting humans back to the Moon, the two liquid-water environments beyond Mars are getting almost as much astrobiology attention as Mars itself. Although Cassini has found that Enceladus is spewing a geyser of water and ice into space, coating itself and feeding Saturn's E ring in the process (AW&ST Mar. 13, p. 27), perhaps the most tantalizing of the Solar System's water reservoirs will literally be a tough nut for explorers to crack.
Scientists have focused on Europa since the Galileo probe sent back strong evidence that there is an ocean of liquid water deep beneath its frozen surface. Because life could exist in that ocean, sending an orbiter to Europa is the highest "flagship-mission" priority for Solar System exploration growing from the National Research Council's 2003 decadal survey. That mission was left out of NASA's Fiscal 2007 budget request, but many scientists at AbSciCon 2006 said it will be necessary to get much closer than orbit, anyway, to detect the signatures of life on Europa, if they exist.
Strawman Europa-orbiter studies using today's technology suggest there could be more than 300 kg. (660 lb.) of payload capacity available for a lander to ride piggyback on an orbiter. But getting a meaningful set of instruments down to the surface would be a challenge. There is no atmosphere, so parachutes are out (although engineers have studied an airbag-cushioned drop from about 0.6 mi.). And organic molecules in the exhaust of retro-rockets for soft landing could throw off the results of sensors designed to look for them.
"YES, YOU CAN HAVE a lander, but because of all the constraints you end up with very little payload at the end because you [address] all of these engineering issues,"
said Tibor Balint of the Jet Propulsion Laboratory.
Even while astrobiologists debate the most scientifically promising spot to land, the rugged terrain visible in the highest-resolution Galileo images of Europa suggests finding a relatively flat landing site would also be difficult. Because intense radiation is believed to have sterilized the surface down to a depth of at least 1.5 meters (5 ft.), some engineers think a high-speed impactor like the copper projectile used in the Deep Impact mission to the comet Tempel 1 would be more effective.
Gravity would pull ejecta from an impact back to the surface much more quickly than was the case on Tempel 1, says Charles Hibbitts of the Johns Hopkins University Applied Physics Laboratory. That would give sensors on the mothership a relatively short time to look for organic compounds in the debris cloud. But, as was the case with Deep Impact, a whole range of space telescopes could be programmed to analyze a debris cloud from Europa, particularly in the productive infrared wavelengths.
"If the James Webb Space Telescope is operational at that time, then it could make supporting observations" similar to those made by the Spitzer Space Telescope during the Tempel 1 impact, Hibbitts says.
