Study Suggests Prospect of Recent Underground Volcanism on Mars

Researchers argue there needs to be an underground source of heat for liquid water to exist underneath the planet's south polar ice cap, as predicted by a previous study.

The Martian South Pole. A new study in Geophysical Research Letters argues there needs to be an underground source of heat for liquid water to exist underneath the polar ice cap.

A study published  last year in the journal Science suggested liquid  water is present beneath the south polar ice cap of Mars. Now, a new study in the journal Geophysical Research Letters argues there needs to be an underground source of heat for liquid water to exist underneath the polar ice cap.

The new research does not take sides as to whether the liquid water exists. Instead, the authors suggest recent magmatic activity- the formation of a magma chamber within the past few hundred thousand years - must have occurred underneath the surface of Mars for there to be enough heat to produce liquid water underneath the kilometer and a half thick ice cap.  On the flip side,the study's authors argue that if there was not recent magmatic activity underneath the surface of Mars, then there is not likely liquid water underneath the ice cap.

"Different people may go different ways with this, and we're really interested to see how the community reacts to it," said Michael, an associate staff scientist in the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper.

The potential presence of recent underground magmatic activity on Mars lends weight to the idea that Mars is an active planet, geologically speaking. That fact could give scientists a better understanding of how planets evolve over time.

The new study is intended to further the debate around the possibility of liquid water on Mars. The presence of liquid water on the Red Planet has implications for potentially finding life outside of Earth and could also serve as a resource for future human exploration of our neighboring planet.

"We think that if there is any life, it likely has to be protected in the subsurface from the radiation," said Ali Bramson, a postdoctoral  research associate at the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper. "If there are still magmatic processes active today, may be they were more common in the recent past and  could supply more widespread basal melting. This could provide a more favorable environment for liquid water and thus, perhaps, life."

Examining the environment

Mars has two giant ice sheets at its poles, both a couple of kilometers thick. On Earth it is common for liquid water to be present underneath thick ice sheets, with the planet's heat causing the ice to melt where it meets the Earth's crust.

In a paper published last year in Science, scientists sad they detected a similar phenomenon on Mars. They claimed radar observations detected evidence of liquid water at the base of Mar's south polar ice cap. However the Science study did not  address how the liquid water could have gotten there.

Mars is much cooler than Earth so it was unclear what type of environment would be needed to melt the ice at the base of the ice cap. Although previous research has examined if liquid water could exist at the base of Mar's ice caps, no one had yet looked at the specific location where the Science study claimed to have detected water.

"We thought there was a lot of room to figure out if is real, what sort of environment would you need to melt the ice in the first place, what sort of temperatures would you need, what sort of geological process  would you need?Because under normal conditions, it should be too cold."

Looking for the heat 

The new study's authors first assumed the detection of liquid water underneath the ice cap was correct and then worked to figure out what parameters were needed for the water to exist. They performed physical modeling of Mars to understand how much heat is coming out of the interior of the planet and if there could be enough salt at the base of the ice cap to melt the ice. Salt lowers the melting point of ice significantly so it was thought that salt could have led to melting at the base of the ice cap.

The model showed salt alone would not raise the temperature high enough to melt the ice. Instead, the authors propose there needs to be additional heat coming from Mars interior. 

One plausible heat source would be volcanic activity in the planet's subsurface. The study's authors argue that magma from the deep interior of Mars rose towards the planet's surface about 300,000 years ago. It did not break the surface, like a volcanic eruption, but pooled in a magma chamber below the surface. As the magma chamber cooled, it released heat that melted the ice at the base of the ice sheet. The magma chamber is still providing heat to the ice sheet to generate liquid water today.

The idea of volcanic activity on Mars is not new-there is a lot of evidence of volcanism on the planets surface. But most of the volcanic features on Mars are from millions of years ago, leading scientists to believe volcanic activity below and above the planet's surface stopped long ago.