In August, when Mars was at its closest approach to Earth in recorded history, did astronomers learn a lot about that planet?

Although Mars made a spectacular appearance in the Summer sky and certainly allowed many outstanding photos to be taken by Hubble (http://hubblesite.org/newscenter/archive/2003/22/) and ground-based telescopes, these observations did not answer any of the fundamental questions about the still-mysterious red planet. "Closest" is very much a relative term. Compared to other near approaches of Mars to Earth even within the past century, this approach was not dramatically closer. In fact, it has been compared to driving from the east side of a U.S. city to the west side and thinking how much closer that brings us to Japan. It is really not that much different. Even this year, Mars remained a distant object.

What has made a dramatic difference in our knowledge of Mars is spacecraft sent from Earth. Starting with the Mariner and Viking flybys and landers, and extending through the Mars Pathfinder (with the little Sojourner Rover) and Mars Global Surveyor, these missions to Mars have added immensely to the knowledge of Mars, and also to some of the mystery. Evidence has been found that there was once liquid water on the surface, but what happened to it remains in question. A remnant magnetic field was found, also. None of these missions answered the big question of whether there was (or is) any life on Mars. See http://mars.jpl.nasa.gov/MPF/index1.html and http://mpfwww.jpl.nasa.gov/mgs/index.html for some of these results.

Now there is an armada of new spacecraft on their way to Mars:

A European mission, Mars Express

http://sci.esa.int/science-e/www/area/index.cfm?fareaid=9

A U.S. mission, Mars Exploration Rover, with two probes, Spirit and Opportunity

http://mars.jpl.nasa.gov/mer/

All these are scheduled to arrive at Mars at the end of 2003 or early in 2004. With a wide variety of instruments, these will be the next sources of information about Mars. This Winter should be a very exiting time for Mars watchers.

This week's question comes from Dr. Dave Thompson. Dr. Thompson is an astrophysicist who studies gamma rays in the Laboratory for High Energy Astrophysics. He helped build, test, and analyze data from EGRET on the Compton Gamma Ray Observatory, and he is now helping build part of the Gamma Ray Large Area Space Telescope (GLAST), scheduled for launch in 2006. His particular scientific interest is gamma-ray pulsars.