Mars size versus earth
Pro Research Analysisby 
Searched over 200M research papers
Comparative Analysis of Mars and Earth: Size and Physical Characteristics
Mars and Earth: Orbital and Rotational Periods
Mars, the fourth planet from the Sun, orbits at a distance of approximately 230 million kilometers from the Sun and has an orbital period of 687 Earth days. In contrast, Earth, the third planet from the Sun, completes its orbit in 365 days. The rotational period of Mars is slightly longer than that of Earth, with a Martian day (sol) lasting 24 hours and 40 minutes, compared to Earth's 24-hour day 15.
Size and Mass Differences
Mars is significantly smaller than Earth. Mars has a diameter of about 4,399 miles (7,081 kilometers), whereas Earth’s diameter is approximately 7,918 miles (12,742 kilometers) . This makes Mars roughly half the size of Earth in terms of radius. Consequently, Mars has only about one-tenth the mass of Earth, which results in a surface gravity that is approximately 37.6% that of Earth's 15.
Density and Surface Area
Mars is less dense than Earth, contributing to its lower mass despite its relatively large size. The surface area of Mars is almost as large as the land surface area of Earth, given that Mars has no oceans . This means that while Mars is smaller in volume, its land area is comparable to Earth's continents.
Formation and Growth
The smaller size of Mars compared to Earth and Venus has been a subject of interest in planetary formation studies. Recent models, such as the Viscous Stirred Pebble Accretion (VSPA), suggest that Mars' growth was stunted due to inefficiencies in the accretion process beyond 1.5 astronomical units (AU) from the Sun. This model helps explain why Mars did not grow as large as Earth . Additionally, Mars is considered a planetary embryo that rapidly accreted and reached about half of its present size in a very short time, possibly escaping further collisions and mergers that would have increased its size .
Atmospheric and Surface Conditions
Mars has a much thinner atmosphere compared to Earth, with a surface pressure of about 0.6 kPa, predominantly composed of carbon dioxide (95%). In contrast, Earth's atmospheric pressure is 101 kPa, with a nitrogen-oxygen composition. The lower atmospheric pressure on Mars contributes to its inability to retain significant amounts of water on its surface .
Water Content and Geological Implications
Earth has a significant amount of water both on its surface and within its mantle, with at least 150 ppm water in the mantle. Mars, however, has a much drier mantle, containing no more than about 35 ppm water. This difference is partly due to Mars' smaller size and greater distance from the Sun, which may have prevented the melting of its surface during accretion, thus limiting the integration of water into its interior .
Conclusion
In summary, Mars and Earth differ significantly in size, mass, density, and atmospheric conditions. Mars' smaller size and mass result in lower surface gravity and a thinner atmosphere. The differences in their formation and growth processes, as well as their water content, highlight the unique evolutionary paths of these two terrestrial planets. Understanding these differences provides valuable insights into the dynamics of planetary formation and the conditions necessary for sustaining life.
Sources and full results
Most relevant research papers on this topic