(First published, May 21, 2001)
By the time you finish reading this sentence, you'll be over 30 miles (50 kilometers) closer to the Red Planet.

Why Mars Is So Close

Click hereto see a Flash graphic that illustrates how a planet lines up when it's at opposition, conjunction and other positions.

Mars & Earth Converge: Watch video animation of this month's planetary event. [ACTIVATE]

Earth and Mars are converging at 22,000 miles per hour (10 kilometers per second) as the pair head for a close encounter this month. On June 21st Mars will lie just 42.3 million miles (68 million kilometers) from Earth -- the nearest it's been in a dozen years.

"The next few months will be a great time to look at Mars," said astronomy professor George Lebo, a NASA summer faculty fellow at the Marshall Space Flight Center. "You won't need a telescope to see it. By early June, Mars will outshine everything except Venus, the Moon and the Sun itself."

The Red Planet grew brighter as it approached opposition on June 13th, the date when Earth and Mars are lined up on the same side of the Sun.

Mars is already a brilliant morning "star." Early rising observers in the Northern Hemisphere can spot the rust-colored orb about 30 degrees above the southern horizon. Sky watchers south of the equator will see Mars arcing high overhead before dawn. In either hemisphere, the planet is easy to pick out near the spout of the teapot-shaped constellation Sagittarius. Mars is bright and doesn't twinkle like a real star -- its steady copper-hued gaze is unmistakable.

In the weeks ahead, the Red Planet will grow even brighter as it approaches opposition on June 13^th -- the date when Earth and Mars are lined up on the same side of the Sun. Astronomers call the arrangement opposition because Mars and the Sun will lie on opposite sides of our planet's sky. Mars is at opposition once every 26 months.

If the orbits of Mars and Earth were perfectly circular, then the distance between two planets would be least at the moment of opposition. But that's not the case. Earth's orbit is slightly elliptical and the Martian orbit is substantially more so. As a result, our closest approach to Mars won't happen until eight days later on June 21st.

At opposition, Mars will no longer be a morning star -- it'll be a dazzling "all-nighter," rising near sunset and reaching its highest point in the sky at midnight. Modest telescopes will reveal normally invisible details including Martian clouds and icy polar caps.

Throughout the coming months Mars will linger in a region of the sky that's home to the very center of our galaxy. This will be a treat for dark-sky observers who can see the faint Milky Way, a hazy band of stars that bisects the sky along the galactic plane. The Milky Way cuts through Sagittarius and brightens near the spout of the teapot -- right by Mars! There lies the galactic center, the lair of a supermassive black hole around which our entire pinwheel galaxy spins.

Despite their proximity in the sky, Mars and the galactic center are really very far apart. A spacecraft from Earth traveling at light-speed would arrive at the Red Planet in only a few minutes. Reaching the inner regions of our galaxy would take an extra 30,000 years!

If spacecraft could travel at the speed of light, we could visit Mars any time we wished. However, NASA's even most advanced propulsion systems aren't quite at that point. We have to choose our opportunities carefully and visit Mars when the planet is nearby -- in other words, at opposition.

NASA's latest Mars probe, 2001 Mars Odyssey, blasted off on April 7th and is hurtling toward the Red Planet even faster than we are. Earth's approach will slow and then reverse as Mars reaches opposition in June, but Mars Odyssey will continue until it enters Mars' orbit on October 24th. During the probe's two and a half year mission, it will monitor space radiation, seek out underground water and identify interesting minerals on the Martian terrain.

Because of Mars' eccentric orbit, not all oppositions are alike. At the next one, on August 28, 2003, Mars and Earth will be just 34.8 million miles (56 million kilometers) apart -- closer than any opposition since 1924. It will be the perfect time to send a new batch of robotic explorers to Mars. Indeed, NASA plans to launch a pair of Mars Exploration Rovers in 2003 and the European Space Agency (ESA) will send a lander of its own -- the Beagle 2 -- which will ride to Mars onboard the ESA's Mars Express orbiter mission.

Meanwhile, don't miss the ongoing show. Mars is out there now, fiery red and beckoning from your own backyard!

Related Pages: Daily Spacewatch Report | Mars Headlines

Tony Phillips writes for science.nasa.gov.