Water is essential for life, on Earth and other planets but Mars has no liquid water on its surface today. New research from Washington University in St. Louis suggests a fundamental reason: Mars may be just too small to hold on to large amounts of water.
The study (Proceedings of the National Academy of Sciences)
used stable isotopes of the element potassium to estimate the presence, distribution and abundance of volatile elements on different planetary bodies. Potassium is a moderately volatile element, but the scientists decided to use it as a tracer for more volatile compounds, such as water.
They measured the potassium isotope compositions of 20 previously confirmed Martian meteorites and determined that Mars lost more potassium and other volatiles than Earth during its formation.
The researchers found a well-defined correlation between body size and potassium isotopic composition. The finding of the correlation of potassium isotopic compositions with planet gravity is a novel discovery with important quantitative implications for when and how the differentiated planets received and lost their volatiles, Dr. Katharina Lodders from Washington University and a coauthor of the study said in a release.