Moving Mars

For Ray Bradbury

A day on Mars is a little longer than a day on Earth: 24 hours and 40 minutes. A year on Mars is less than two Earth years: 686 Earth days, or 668 Martian days. Mars is 6,787 kilometers in diameter, compared to Earth’s 12,756 kilometers. Its gravitational acceleration is 3.71 meters per second squared, or just over one-third of Earth’s. The atmospheric pressure at the surface of Mars averages 5.6 millibars, about one-half of one percent of Earth’s. The atmosphere is largely composed of carbon dioxide. Temperatures at the “datum” or reference surface level (there is no “sea level,” as there are presently no seas) vary from -130° to +27° Celsius. An unprotected human on the surface of Mars would very likely freeze within minutes, but first would die of exposure to the near-vacuum. If this unfortunate human survived freezing and low pressure, and found a supply of oxygen to breathe, she would still be endangered by high levels of radiation from the sun and elsewhere.

After Earth, Mars is the most hospitable planet in the Solar System.