Question

Is it true that the ancient Martian atmosphere may have been like Earth’s today?

Yes. In fact, many scientists believe that the Earth presents a modern picture of Mars in its distant past. While both planets were formed around the same time (4.5 billion years ago) and consist of similar elements, only the Earth has remained habitable due to the preservation of its dense atmosphere. However, geological data suggests that the Martian atmosphere may have looked somewhat like Earth’s atmosphere today (warm and wet), consisting of an abundance of water, CO2, and nitrogen. Likewise, evidence suggests that the mean surface temperatures of Mars were at or above freezing. The initial conditions of Earth include similar conditions, though the Earth’s surface was more volatile than that of the early red planet. Scientists even predict a future for Earth that looks a bit like Mars today. See the table below for details. Several Member Institutes of the NASA Astrobiology Institute have been instrumental in our efforts to understand the early conditions of terrestrial planets. Check out Harvard University's website for information on the early Earth: http://www.oeb.harvard.edu For reasons why Mars no longer sustains a warm wet atmosphere, check out http://www-mgcm.arc.nasa.gov/mgcm/faq/wetmars.html Water Earth: oceans Mars: Evidence for surface liquid water; possible hydrological cycle Temperature Earth: >273K Mars: ~273K Atmosphere Earth: CO2, N2, H2O: >1 atm Mars: CO2, N2(?), H2O: ~1atm Volcanic and geothermal activity? Earth: Yes, Mars: Yes Geochemical carbon cycle Earth: Reactions in water Subduction and volcanism Mars: Reactions in water early volcanism only Duration of dense atmosphere Earth: 4.5 Gyr to present Mars: 4.5 Gyr to 3.5 Gyr possibly Preservation of rock record Earth: Highly altered and reworked Mars: ~2/3 of surface is older than 3.8 Gyr Biology Earth: Diverse life by 3.5 Gyr Mars: unknown
April 30, 2002