Mars continues to puzzle planetary scientists with its small mass relative to Earth and Venus. This discrepancy has sparked debate over the planet’s potential for surface water, oceans, and life. According to Carnegie Institution planetary scientist George Wetherill, Mars’ mass is roughly a tenth that of Earth, earning it the nickname “small Mars problem.”
Several hypotheses have been proposed to explain why Mars ended up smaller than its counterparts. One theory suggests that Jupiter’s migration inward toward the Sun disrupted the formation of Mars, potentially limiting its growth in mass. Another hypothesis proposes that Mars received little material from the Main Asteroid Belt, hindering its ability to grow larger. A third model suggests that early instability in the solar system led to the perturbation of building blocks, preventing their coalescence into a planet of Mars’ size.
Planetary scientists Sean Raymond and Stephen Kane emphasize the importance of mass as a fundamental property of planets. They argue that Mars’ small mass contributed to its loss of water and habitability. The red planet’s geological history and volcanic activity were limited due to its small size, making it susceptible to atmospheric stripping by the solar wind.
Matthew Clement notes that whatever the source of Mars’ size difference must have occurred early on in the solar system’s history, within a few million years. Solving this conundrum is crucial for understanding why our solar system has four vastly different planets, including Earth and Venus. By studying the formation of planets from dust and continued observations of young stars, scientists can gain insights into this process.
Kane suggests that the unusual architecture of our solar system might allow for the formation of numerous Venus- and Earth-size planets beyond what we see today. This could be beneficial for astrobiology, as giant planets are relatively rare.
Source: https://www.forbes.com/sites/brucedorminey/2024/12/30/mars-small-mass-still-puzzles-planetary-scientists