Sibling Rivalry: A Mars/Earth Comparison
Scientific understanding is often a matter of making the right comparisons. In terms of studying the Earth, one of the best comparative laboratories exists one planet over--on Mars. In many ways, the study of Mars provides Earth bound scientists with a control set as they look at the processes of climate change, geophysics, and the potential for life beyond our own planet. In January of 2004 NASA landed two extraordinary research probes on Mars as part of an international armada of exploratory vehicles sent to Earth's dusty neighbor. Much of the technology and scientific methodology built into those missions directly relate to the sophisticated research efforts currently being used to study our own planet.
The similarities are striking. Each planet has roughly the same amount of land surface area. Atmospheric chemistry is relatively similar, at least as Earth is compared to the other planets in the solar system. Both planets have large, sustained polar caps and the current thinking is that they're both largely made of water ice. The sibling planets also show a similar tilt in their rotational axises, affording each of them strong seasonal variability. The neighbors also present strong historic evidence of changes in climate.
Some Basic Facts about Mars: Ave. Solar Distance: 227,940,000 km (1.52 AU) Diameter: 6,794 km - Rotational Period (one day): 24.622 hours Mean Surface Temp: -63_ C - Orbital Period (one year): 686.98 days - Moons: 2 (Phobos and Demios) - Gravity: 38% Earth. Some Basic Facts about Earth - Ave. Solar Distance: 149,600,000 km (1AU) Diameter: 12756.34 km - Rotational Period (one day): 23 hours, 57 minutes Mean Surface Temp: 14_ C - Orbital Period (one year): 365.242 Earth days Moons: 1 (Luna) - Gravity: 9.78 (m/s2) Earth
NASA Goddard Space Flight Center