Scientists have finally discovered what’s hidden inside mysterious blobs buried underneath the Red Planet’s equator, and the answer could help in planning for life on Mars.
Stretching several kilometres beneath the planet’s surface, scientists have discovered ice using new data from ESA’s Mars Express spacecraft.
This is not the first time the spacecraft has visited this part of the planet, but the first time it raised more questions than answers. Fifteen years ago, Mars Express studied the wind-sculpted Medusae Fossae Formation where the ice has now been found.
Back then, Mars Express revealed that there were massive deposits estimated to be 2.5km (1.6 miles) deep under the formation – but no one knew what these deposits contained. Now, scientists have an answer – and results that show the deposits are thicker than they thought at an incredible 3.7km (2.3 miles) deep.
In fact, the spacecraft discovered so much ice there that, if it all melted, it would cover Mars in a layer of water 1.5 to 2.7m (4.9 to 8.9ft) deep. That’s enough water to fill Earth’s Red Sea.
“Excitingly, the radar signals match what we’d expect to see from layered ice, and are similar to the signals we see from Mars’s polar caps, which we know to be very ice-rich,” said Thomas Watters of the Smithsonian Institution, USA, lead author of the research.
Published in the journal Geophysical Research Letters, the findings mark the discovery of the most water ever found in this part of the Red Planet. The water could be key to future human missions to Mars, which would land near the equator rather than the ice-rich polar caps.
"While this news of finding layers of water ice within the dusty subsurface of Mars does not provide any new optimism for finding alien life on Mars, it could help humans be the aliens on Mars in the future," Dr Darren Baskill, astronomy lecturer at the University of Sussex, told BBC Science Focus.
"Mars was once a wet planet, but liquid water no longer exist there. So while this large source of water-ice deposits is hundreds of meters underground, its location near the equator is convenient, and raises the prospect of this water-ice being mined in the future, making human exploration of Mars that little bit more viable."
But separating the ice from its dusty surroundings could be tricky. After all, the Medusae Fossae Formation is essentially a load of windswept piles of dust.
This is also what made it so tricky to find out what was inside it. Rather than ice, there was a possibility that the deposits were simply more dust – but the new radar data has narrowed it down.
“Given how deep it is, if the MFF [Medusae Fossae Formation] was simply a giant pile of dust, we’d expect it to become compacted under its own weight,” said co-author Andrea Cicchetti of the National Institute for Astrophysics, in Italy.
“This would create something far denser than what we actually see… and when we modelled how different ice-free materials would behave, nothing reproduced the properties of the MFF – we need ice.”
What is most likely, is that the formations are instead made of layers of dust and ice, where an outer layer of dust protects the ice from melting.
Since the ice is at the planet’s equator, it could not have formed in Mars’ present-day climatic conditions. This suggests the ice is a remnant of a previous epoch – challenging what scientists currently understand about the Red Planet’s climate history and raising even more questions for future research.
About our expert
Dr Darren Baskill is an outreach officer and lecturer in the department of physics and astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
Read more: