14 DAY TRIAL // Recent data returned to Earth by NASA spacecraft orbiting the Red Planet are providing new evidences to a hypothesis suggesting that Mars may still feature a liquid water cycle, at least over some parts of its surface. This idea is based on studies of seasonal, finger-like landscape structures.
NASA is currently operating the Mars Reconnaissance Orbiter (MRO) and the Mars Odyssey spacecraft in orbit around our neighboring world. Together, these vehicles are painting an incredibly detailed picture of the seasonal variations occurring at the Red Planet every year.
The seasonal features they are seeing are currently the strongest indicators that liquid water still exists on the surface of Mars. These structures are dark, long and slender, and they tend to emerge on various slopes whenever temperatures rise at their respective locations.
Scientists believe that this may be indicative of frozen chemicals thawing when temperatures rise high enough. As this happens, the liquid – potentially water – heads down across the slopes, giving rise to the narrow canals that can be seen from space as they appear and disappear with the seasons.
MRO and Mars Odyssey have thus far been able to determine that these seasonal changes are also accompanied by iron minerals variations across the same slopes that host the landscape features – which are known among planetary scientists as recurring slope lineae (RSL).
These RSL, experts argue, may be carved out by brines (very salty liquids) that contain antifreeze agents, including iron minerals like ferric sulfate. Though other explanations for RSL exist, many planetary scientists believe that these features form as liquids flow on the surface of Mars.
“We still don't have a smoking gun for existence of water in RSL, although we're not sure how this process would take place without water,” explains Georgia Institute of Technology (Georgia Tech) graduate student Lujendra Ojha, who is the lead author of two reports on the seasonal flows.
Ojha and James Wray, a Georgia Tech assistant professor, are investigating RSL photographed by the High Resolution Imaging Science Experiment (HiRISE) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instruments on MRO.
“Just like the RSL themselves, the strength of the spectral signatures varies according to the seasons. They're stronger when it's warmer and less significant when it's colder,” Ojha explains.
“The flow of water, even briny water, anywhere on Mars today would be a major discovery, impacting our understanding of present climate change on Mars and possibly indicating potential habitats for life near the surface on modern Mars,” says Richard Zurek, an MRO project scientist with the NASA Jet Propulsion Laboratory (JPL) in Pasadena, California.