At first glance, Mars looks like an unchanging world.
Rovers on the surface of the planet have beamed back images of fragile rock features that appear to levitate off the ground, seemingly untouched by the elements for thousands of years at a time.
Unlike Earth, which has an ever-changing landscape as seen from space, on Mars only wisps of clouds move above the planet, with the occasional dust storm whirling across its surface.
For the most part, Mars has persisted as a seemingly static red orb, barely changing from day to day.
However, once you look past the Martian surface, the geology tells a different story.
A new study published Thursday in the journal Science provides evidence that the red planet was a wildly different place as recently as 370,000 years ago.
At that time, Mars was likely in its most recent ice age, the study found.
Earlier studies modeling the red planet’s past climate revealed that Mars has been through ice ages like Earth, but thanks to this new study tracking ice deposition in the north pole since the last ice age, scientists now have a more specific date for Mars’ dramatic climate changes.
Mars: The white planet?
“Mars is not a static place,” said Isaac Smith, the co-author of the new study, in an interview.
“Future astronomers are going to see a very different place.”
Thanks to work done by NASA’s Curiosity rover, researchers know that at least some parts of Mars were once habitable millions of years ago.
While this new ice cap work doesn’t necessarily change our understanding of Martian habitability in the distant past, it does help scientists further refine what Mars looked like thousands of years in the past, and help predict what it may look like thousands of years in the future.
“If we were to look at Mars 150,000 years in the future or 400,000 years in the past, it would look very different to us,” Smith said.
Image of Mars showing ice age advancement and retreat.
Image: ESA/DLR/FU-Berlin/Ralf Jaumann
“The Mars we know now, it wouldn’t resemble the other one. That’s because if you take a bunch of ice on the north pole and you redistribute it over the planet, the planet’s going to turn white. So we’re going to have white Mars instead of red Mars.”
Scientists have long known that, like Earth, Mars goes through changes in its global climate due to the tilt of the planet’s axis and relatively small changes in its orbit around the sun.
Smith and his team were able to date the ice age thanks to radar data gathered by the Mars Reconnaissance Orbiter, a spacecraft which has been orbiting Mars for 10 years.
“It [the new study] makes an appropriate use of the SHARAD [the radar instrument on the MRO] data,” said Roberto Seu, lead scientists for the SHARAD instrument on board the orbiter, via email.
Seu is unaffiliated with the new study.
“This is a very important, original and unique work,” he said.
Mars as a ‘simplified laboratory’ for Earth
The scientists found that since the end of Mars’ last ice age about 370,000 years ago, approximately 87,000 cubic kilometers of ice has built up at the poles.
This exact measurement will allow researchers to produce better climate models of Mars and maybe even tell us something about Earth.
Radar is also used to look at ice thickness at Earth’s poles.
“Mars is kind of a simplified laboratory for understanding the Earth. Mars doesn’t have oceans and it doesn’t have biology,” Smith added.
“Because of that, the physics is actually more straight forward, and we can refine our understanding of Martian physics to improve our understanding of Earth’s physics.”
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