The Phoenix spacecraft that recently landed on Mars is getting a lot of attention in the media.
This NASA mission left Earth about 9 months ago and successfully landed a spacecraft near Mars’ north polar cap on June 25, 2008. Using a scoop on the end of a 7-foot arm, Phoenix has and will continue to dig down below the surface to investigate if there is frozen water and other conditions that might have supported life. You can read about the details of the mission here
The event of its safe landing was of special interest to me. My group at NASA’s Jet Propulsion Laboratory helped build the navigation equipment used to guide Phoenix to its landing spot and the receiving equipment used to follow the spacecraft during its entry, decent, and landing (EDL) on the surface of Mars. Besides the original launch, EDL is the most dangerous phase of the mission because any error in performance can be catastrophic. Our EDL equipment does not prevent such a catastrophe but provides information that can be used in future designs as to where and how the potential failure may have taken place. Fortunately, this landing was a success.
Because one of the goals of this mission is to search for the signatures of life, it is critical that the spacecraft itself does not bring life from Earth to contaminate Mars. I have written earlier about the efforts taken to build the spacecraft in a clean environment and the difficulty in keeping it bacteria-free. At least two recent news articles have called attention to the problem, one in Nature and another in The New Scientist.
As reported in the second article, just before the launch in August 2007, tests showed the presence of at least 26,000 cells per square meter of area in the lab representing about 100 kinds of bacteria. While this amount is very small compared with billions of bacteria in a normal environment, it still poses an obstacle for a mission seeking for a rare signature of life. When these remaining bacteria were tested for their ability to tolerate heat, cold, salt and radiation, one species, called Bacillus pumilus survived doses of UV radiation that killed nearly all other life. While every effort has been made to reduce the chances of contamination of Mars with Earth life, scientists for the mission acknowledge that “there is a possibility you’d get contamination, but the probability is very low.”
RTB scholars posit that, now or in the future, life will be found on Mars. However, its source will not likely be contamination from a man-made spacecraft but, instead, a naturally formed spacecraft—namely, a meteorite blasted off of Earth by a collision with a large asteroid or comet sometime in the past. Since Earth is teeming with life it is not unreasonable to consider that some of this life made its way to Mars in such a fashion. In the RTB model, life on Earth came about not by natural processes, but by the acts of God who created with a purpose.