Mars May Be Too Small to Retain Water and Support Life

Are NASA, the other space agencies and private space companies wasting their time focusing on finding signs of life on Mars and using this to justify and/or air creating human settlements there? That may be the case if you listen to researchers from the Washington University in St. Louis who say size matters when it comes to life on other planets and Mars is just too small to have it or sustain it because it’s too tiny to have water.

“Mars’ fate was decided from the beginning. There is likely a threshold on the size requirements of rocky planets to retain enough water to enable habitability and plate tectonics, with mass exceeding that of Mars.”

In a university press release announcing the publication of a new study in the Proceedings of the National Academy of Sciences, Kun Wang, assistant professor of earth and planetary sciences in Arts & Sciences and senior author of the study explains how his team reached its conclusion about Mars being more like a dried pit than a juicy life-supporting olive. While the non-natural water-filled ‘canals’ that astronomers of the 19th and 20th centuries believed they saw on the Martian surface have been proven to be optical illusions, Martian rocks and Martian meteors found on Earth show solid evidence that the planet once had natural rivers and channels. However, the most recent explorations have found no water on the Martian surface. Wang and his colleagues turned to an unexpected element to resolve this discrepancy – potassium (K).

“This study presents K isotope data from a spectrum of martian lithologies as an isotopic tracer for comparing the inventories of highly and moderately volatile elements and compounds of planetary bodies. Here, we show that meteorites from Mars have systematically heavier K isotopic compositions than the bulk silicate Earth, implying a greater loss of K from Mars than from Earth.”

The team used stable isotopes of potassium (K) to estimate volatile elements and compounds — including water — on planets, satellites and large asteroids. They found that Mars, Earth, the Moon and the asteroid 4-Vesta had large amounts of volatile elements compounds when they were formed, but Mars lost more than Earth, and the Moon and 4-Vesta lost more than both. The evidence pointed to size as the deciding factor for how much water a planet or space rock retained. For the Red Planet, Wang says the key was the Martian meteorites found on Earth.

“Those Martian meteorites have ages varying from several hundred millions to 4 billion years and recorded Mars’ volatile evolution history. Through measuring the isotopes of moderately volatile elements, such as potassium, we can infer the degree of volatile depletion of bulk planets and make comparisons between different solar system bodies.”

Wang points out that those meteorites also dispute a prevailing theory that Mars once had even more water than Earth. As a result, astronomers now have an easy technique for determining if an exoplanet in a star’s habitable “Goldilocks” zone is a good prospect for life.

“The size of an exoplanet is one of the parameters that is easiest to determine. Based on size and mass, we now know whether an exoplanet is a candidate for life, because a first-order determining factor for volatile retention is size.”

Which brings us back to Mars. Although it’s in the Sun’s habitable zone, this study’s results make Mars too small to retain water for life. Should space agencies and companies move on to another planet or Moon? Good luck convincing them to abandon exploring the planet that has captured the imagination of astronomers and science fiction fans for centuries. Venus may be closer, but they can at least see where they’re going on Mars. Even if it doesn’t have enough water, the experience will prepare space travelers for the next longer mission to a better candidate.

Sorry, Mars … size matters.