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EARTH vs MARS
Mars is about half the size of Earth by diameter and has a much thinner atmosphere,
with an atmospheric volume less than 1% of Earth’s. The atmospheric composition is
also significantly different: primarily carbon dioxide-based, while Earth’s is rich in
nitrogen and oxygen. The atmosphere has evolved: evidence on the surface suggest
that Mars was once much warmer and wetter.
On Earth, living organisms release much of the planet’s methane. It is also the main
component of naturally occurring hydrocarbon gas reservoirs, and a contribution is also
provided by volcanic and hydrothermal activity. Because of the key role natural biology
plays in Earth’s methane production, confirming the existence of methane on Mars, and
distinguishing between its potential sources, is a top priority of the ExoMars Trace Gas
Orbiter.
