Greenhouse gases lurking in the form of icy clouds on ancient Mars are likely indirectly responsible for the red planet’s earliest rivers and lakes, says a new study just published in the journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
“Despite receiving just 30
percent of Earth’s present-day solar insolation, Mars had water lakes and
rivers early in the planet’s history, due to an unknown warming mechanism,” the
authors write. “A possible explanation is warming by water ice clouds,”
they note.
A thin layer of icy,
high-altitude clouds, not unlike cirrus clouds on Earth, could have warmed
Mars’ atmosphere sufficiently to cause a greenhouse effect. University of
Chicago planetary scientist Edwin Kite, the paper’s lead author, says he and
colleagues’ new climate model helps cement the idea of a warm, young
Mars.
“It's been known for many
years that CO2 alone is not enough to explain warm climates on Early Mars;
there must have been strong non-CO2 greenhouse warming,” Kite told me.
Problem
is, what was the source of the non-CO2 warming?
“Our work supports the
hypothesis that the warming came from high-altitude water ice clouds,” says
Kite.
And Mars’ geology of
ancient river tracks and lakebeds show that the warming likely persisted
for at least hundreds of years, the University of Chicago reports. But only
if the planet has spatially, patchy surface water sources, say the authors.
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