BY DR EMILY BALDWIN
Posted: 18 March, 2009
Droplets of salty liquid water mixed with mud have been detected on a leg of the Mars Phoenix Lander, according to new research that will be discussed at the Lunar and Planetary Science Conference in Houston next week.
This is the first time liquid water has been detected and photographed outside the Earth, and has implications for the presence of this liquid nectar in other locations on Mars.
Droplets on a leg of the Mars Phoenix lander are seen to darken and coalesce evidence that they are made of liquid water, say some scientists. Image: NASA/JPL-Caltech/ University of Arizona/Max Planck Institute
“A large number of independent physical and thermodynamical evidence shows that saline water may actually be common on Mars,” says Nilton Renno, a University of Michigan professor and a co-investigator on the Phoenix mission. “Liquid water is an essential ingredient for life. This discovery has important implications to many areas of planetary exploration, including the habitability of Mars.”
Because of the planet’s low temperature and atmospheric pressure, scientists had believed that water could only exist on Mars as an ice or vapour, sublimating directly from a solid to gaseous form when conditions permitted. The new analysis shows that this assumption may need adjusting, for the research suggests that the combination of temperature fluctuations in the Martian arctic and salts contained in the soil could create pockets of water too salty to freeze.
The evidence comes from studying images of one of the lander’s legs, which revealed droplets of the curious substance appearing to grow throughout the polar summer. Again, taking into account the local temperature conditions and the salty composition of the soil in Phoenix’s workspace, scientists believe the droplets were most likely a mixture of salty liquid water and mud. Specifically, they think that as the Lander touched down, the rockets that guided it to its location melted the top layer of ice below a thin sheet of soil.
Furthermore, the scientists report that the muddy droplets appeared to grow by absorbing water from the atmosphere. Images suggest that some of the droplets darkened, then moved and merged, physical evidence that they were liquid. Thermodynamic calculations support the rate at which these droplets grew.
Results from the wet chemistry lab showed evidence of perchlorate salts, which likely include magnesium and calcium perchlorate hydrates. These compounds have freezing temperatures of about -56 and -76 degrees Celsius respectively. The temperature at the landing site ranged from approximately -20 to -95 Celsius, with a median temperature around -60 Celsius, but during the first months of the mission, temperatures at the landing site were much warmer. The results have extremely important implications for the possibility of life on Mars, since it is well known that certain bacteria on Earth thrive in extremely salty and cold conditions.
“This discovery is the result of the talent and dedication of the entire Phoenix team and NASA, whose strategy for Mars exploration and the Phoenix mission is ‘follow the water,’” concludes Renno.