Self-portraits taken by a NASA probe on the surface of Mars may have provided our first glimpse of liquid water on another planet. The Phoenix Mars Lander, which touched down near the planet’s north pole, was designed to look only for ice frozen into the Martian soil. But University of Michigan space scientist Nilton Rennó says probe images show blobs of liquid water clinging to the lander’s titanium legs.
In an October paper in the Journal of Geophysical Research, Rennó theorizes that as Phoenix landed, its thrusters displaced topsoil and splashed small droplets of brine onto the probe’s legs. Sodium and magnesium perchlorate salts in the Martian soil may allow water to remain liquid despite the extreme cold, about –90 degrees Fahrenheit. In successive images, the drops seem to flow downward and darken, as if they are melting. “I think there is liquid water on Mars right now,” Rennó says. In a follow-up, he confirmed that under simulated Martian atmospheric conditions, sodium salts do absorb water vapor and form a liquid solution.
Michael Hecht of the Jet Propulsion Laboratory disagrees with Rennó’s assessment, saying the blobs could merely be frost; Phoenix principal investigator Peter Smith of the University of Arizona in Tucson thinks there is not yet enough evidence to evaluate the claim. “Whether you believe Rennó’s case or not, though, he’s created some interesting ideas that are very relevant to future Mars research,” Smith says. One intriguing possibility: If fluid water does persist on Mars, life that might have thrived there millions of years ago, when the climate was warmer and wetter, could be hanging on in thin layers of salty water just beneath the surface.