"But the association of the deposits with the inverted channels and valleys led us to change our thinking in favor of a fluvial"i.e. river- or water-associated"origin for the beds."
Additionally, a spectrometer onboard the Mars Reconnaissance Orbiter identified minerals in the light-toned layered deposits linked to liquid water on Earth.
"Mars Life, Inc."
Andrew Knoll, a Harvard University biologist and member of NASA's Mars program, who was not involved with the new study, called it a welcome paper that "puts another brick in the wall of Mars knowledge."
"Whether it changes the value of stock in Mars Life, Inc., isn't clear," he added.
Weitz also declined to speculate what a longer wet period on the Red Planet might mean for potential life there.
However, the study does appear to extend the window when Mars would have been more hospitable to life.
Prior research by Knoll and other researchers has painted a picture of the Red Planet that, in all but its very earliest years, was too acidic and briny for life as we know it.
Francois Poulet is an astrophysicist at Paris-Sud University in France, who has studied ancient Martian geology.
"There is still an ambiguity in the interpretation of the observed features," he said. "This is very usual in the geology of Mars."
Weitz, the lead study author, agrees that other forcessuch as explosive volcanism, wind deposition, and other geological processesmay explain the layered deposits and mineralogy her team identified.
Knoll, the Harvard scientist, noted that many questions remain about the timing and details of geology on early Mars.
"Very early Mars was surely warmer and wetter than the planet has been subsequently, but how warm and how wet remain to be established," he said.
"The Weitz, et al. work fits within this rubbery framework of uncertainty. We've still got lots of exploration to do."
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