Hold on to your hats and keep a pair of binoculars handy:
After a 26-month sprint around the track of the solar system,
we are about to lap Mars again.

Today, the red planet is in “opposition,” an event that
puts Earth between Mars and the Sun. On June 21, Mars will be
at its closest distance from Earth since 1988, a mere 67.3
million kilometers (approximately 42 million miles). All
summer long, Mars will be brighter than usual, particularly
for sky-watchers in the southern United States and those in
the Southern Hemisphere.

On average, Mars is 50 percent farther from the Sun than
Earth is. Because of its tighter orbit, Earth passes Mars
every couple of years. The reduced distance between the two
planets and better solar illumination angle give Earthlings
the best Mars-viewing opportunity. Through October, Mars will
be easy to spot looking south, especially around midnight. The
better view will be reserved for those living in the Southern
Hemisphere, with Mars high in the sky. In the Northern
Hemisphere, Mars will be low on the horizon. The more south
the observer is, the higher the red planet will appear in the

For centuries these favorable observing conditions have
excited human imagination, providing closer views and new
details and features. Now with better tools and the same
hunger for discovery, NASA’s Jet Propulsion Laboratory is
still paying close attention to Mars’ position to launch
spacecraft at the most favorable opportunity to save fuel and
time. Taking advantage of the upcoming alignment will be the
2001 Mars Odyssey orbiter, the most recent mission to the red
planet, which was launched April 7 and will arrive October 23,

To understand the mechanics of timing launches to Mars,
Dr. E. Myles Standish, a JPL astronomer who specializes in
studies of planetary positions, compares Earth and Mars to two
cars on different nearly circular tracks. The car on the
shorter inside track is going faster, getting ahead of the one
on the outside, and eventually catching up with it and
overtaking it.

“If you were in the car on the inside track and wanted to
throw a ball to someone in the car on the outside, you can do
it only at certain times: you have to throw the ball outward
at a specific time before your car has caught up with the
outside one, and you have to aim at a spot ahead of the
outside car. It is very similar with spacecraft,” Standish

While Martian opposition occurs every other year, the
minimum distance between the two planets is not always the
same because of the elliptical orbits of the two bodies,
particularly Mars. However, this is not a major concern for
mission planning.

“The distance between the two planets is important, but
it doesn’t matter nearly as much as the timing, which is
crucial,” Standish said.

The next Mars opposition will be in August 2003, when the
two planets will be the closest they ever been in at least
5,000 years, approximately 55.7 million kilometers (34.6
million miles). At that time, NASA will send two JPL-built
rovers to Mars, each capable of exploring distances greater
than the Sojourner rover of Mars Pathfinder fame.

For more information about Mars exploration, log on to
http://mars.jpl.nasa.gov .

New pictures illustrating Mars opposition are available

JPL manages the Mars Exploration Program for NASA’s
Office of Space Science, Washington D.C. JPL is a division of
the California Institute of Technology in Pasadena.