Astronomy and Space Science

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The Mars Reconnaissance Orbiter's camera is by far the largest ever sent to Mars, or to any planet other than Earth. With a resolution of twenty-five to thirty-two centimeters per pixel, scientists will be able to identify objects on Mars about one meter across. The Martian Spy Satellite (an Acrobat file) was my editor's title, not mine, but it is appropriate. This article first appeared in Astronomy Now.

Most moons in the Solar System are very small compared to their planets. Ganymede is bigger than the planet Mercury but it must be a grave disappointment to its parent, Jupiter. Even Titan, in spite of its name and for all its methane streams and rain, is positively tiny compared to Saturn. There are two exceptions. Earth's moon weighs in at about 1.2 percent of Earth. Pluto's Charon is ten to fifteen percent of Pluto's mass. Why?

Jupiter's water world Europa is, without doubt, one of the most interesting places in the Solar System. If ever there were a chance of finding familiar carbon-based life, it is in Europa's deep oceans -- under the relatively thin but impenetrable shell of ice. What are the chances of finding evidence for life on the surface where we can see it? (Acrobat file.)

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