• Home
  • /
  • Space
  • /
  • Is Mars Too Small To Retain Surface Water?

Is Mars Too Small To Retain Surface Water?

Artist's impression of a Mars with surface water. Is Mars too small to retain these conditions? Credit: NASA Earth Observatory/Joshua Stevens; NOAA National Environmental Satellite, Data, and Information Service; NASA/JPL-Caltech/USGS; Graphic design by Sean Garcia/Washington University

The modern Red Planet is a harsh, lifeless desert, but geological data show that at one time there was almost more water there than on Earth.

There are plenty of versions about the reasons why Mars lost almost all the resources necessary for the development of life. But now scientists have found a reliable correlation between the size of a celestial body and its ability to retain volatiles. 

Is Mars too small to retain surface water: Everything you need to know


An international team of geologists, oceanographers, and planetary scientists analyzed a whole spectrum of data from both spacecraft that studied Mars from orbit and from rovers that worked on the surface, as well as the results of studying Martian meteorites that hit Earth.

Assessment methods

The assessment method used in the recent study can be considered quite innovative. Usually, to calculate the historical content of volatile elements and compounds (including water) in geological formations, scientists analyze the ratio of certain “markers” – usually potassium and thorium or rubidium and strontium.


But the team led by Kun Wang applied a more accurate method: tracking the concentrations of stable isotopes of potassium alone.


This alkali metal is characterized by moderate volatility, but its presence reliably corresponds to the concentrations of other light elements and chemical compounds. Including, of course, water and organic molecules.

Volatile elements

As a result, an interesting correlation was revealed: Mars has retained much less volatile elements and compounds than Earth, but much more than the Moon and the large asteroid 4-Vesta.

Size of celestial bodies

That is, the ability to retain chemical elements and substances important for the emergence and maintenance of life directly depends primarily on the size of a celestial body. Or rather, from the level of gravity on its surface.

Hypotheses and conclusions

At first glance, the conclusions are obvious, but not so simple. There are many hypotheses explaining why Mars lost almost all water and organic compounds. Some boil down to the absence of a magnetic field in the Red Planet, which allows the solar wind to literally rip valuable molecules out of the atmosphere. And others argue that the fault is the too weak or completely absent tectonics of Mars due to a lack of mass or a large satellite in orbit around it.

Not proven

Each of them can be true – as well as all of them at the same time. But before that, there was no clear statistically proven sign of the planet’s viability depending on its size in the arsenal of planetary scientists.


Now scientists have obtained the lower limit of this value – the “dimensions” of Mars. And apparently, the planet’s habitability has always been limited due to its small size.

Is Mars too small to maintain the necessary conditions?

Planets smaller or slightly larger clearly cannot maintain on their surface the conditions necessary to retain volatiles and compounds. What might be the missing mechanisms is a secondary question, especially in light of the study of exoplanets located at a distance of several light-years from us. Such distances do not allow one to determine the presence or absence of tectonic activity on them, except to roughly estimate the presence of water.

Join the discussion and participate in awesome giveaways in our mobile Telegram group. Join Curiosmos on Telegram Today.


Ogliore, T. (2021, September 21). Mars habitability limited by its small SIZE, Isotope study suggests – the source – Washington University in St. Louis. The Source.
Seo, H. (2021, September 22). Mars may be too small to have ever been habitable. Popular Science.
Smith, A. (2021, September 23). Mars is too small to have ALIENS, scientists suggest. The Independent.
Starr, M. (n.d.). There could be an extremely simple reason Why Mars isn’t as suitable for life. ScienceAlert.
Tian, Z., Magna, T., Day, J. M. D., Mezger, K., Scherer, E. E., Lodders, K., Hin, R. C., Koefoed, P., Bloom, H., & Wang, K. (2021, September 28). Potassium isotope composition of mars reveals a mechanism of planetary Volatile retention. PNAS.