There’s still time for a close encounter with Mars

NASA's Hubble Space Telescope snapped this portrait of Mars within minutes of the planet's closest approach to Earth in nearly 60,000 years. This image was made from a series of exposures taken between 5:35 a.m. and 6:20 a.m. EDT Aug. 27 with Hubble's Wide Field and Planetary Camera 2. In this picture, the red planet is 34,647,420 miles from Earth. Credit: NASA, J. Bell (Cornell U.) and M. Wolff (SSI)

10:05 a.m., Sept. 5, 2003 --On the morning of Aug. 27, Mars came closer to the Earth than at any time during the past 56,000 years, giving astronomers a close up of the red planet and everyone on Earth a spectacle in the night sky.

Harry Shipman, Annie Jump Cannon Professor of Astronomy, a nationally recognized astronomer and teacher who also lectures at the Mount Cuba Astronomical Observatory in Greenville, guided a group of observers as they looked through the Mt. Cuba telescope at Mars last week.

Q: If we didn't see Mars on Aug. 27, will we have to wait 187 years before we can be up close and personal with the red planet?

A: For the next month or so, Mars will be quite well-situated and very much worth a look.

Q: If I were to try to see Mars tomorrow night, assuming the sky is clear, where would I look and what would I be looking for?

A: If you observe after sunset, look toward the southeast. Mars is the very bright copper-colored object. You don't need a road map to see it. During the night, it moves from the southeast, towards south, towards southwest.

Q: At this close approach, Mars is 34.6 million miles from Earth. Can you help us visualize how close this is?

A: Suppose that the Earth were the size of a chickpea, a little over a quarter of an inch in diameter. Mars would then be about the size of a sesame seed, a tenth of an inch in diameter, and would be located 83 feet away. These are the planetary proportions that are demonstrated in the scale model of the solar system on the University campus. So even though this is as close as Mars ever gets, it's not close enough to reach out and touch. The solar system is a very big place. You can find the University’s scale model on the web at [www.museums.udel.edu/art/info/planets.html].

Q: Why did we have to wait 56,000 years for Mars to come this close to Earth? Isn't the planet always the same distance from the sun and the Earth?

A: There are a couple of factors that influence the distance between Mars and the Earth. First, both of these planets circle the sun, with the Earth going a good bit faster. Every couple of years the Earth catches up with Mars and passes it, just as a faster runner can pass a slower runner on a running track. It is at these times that Earth and Mars come close to each other and Mars looks brighter. Mars is the next planet out in the solar system.

The second factor is that both Earth and Mars follow oval, elliptical paths around the sun, rather than strictly circular ones. Planets in elliptical orbits are not always the same distance from the sun. Mars, in particular, varies a good bit in its distance from the sun. And this year, the Earth is passing by Mars just at the point where Mars is closest to the Earth, and the Earth is farthest from the Sun, thus closer to Mars. A good representation of this phenomenon can be found on the web at [http://imgsrc.hubblesite.org/hu/db/2003/22/images/b/formats/web.jpg].

Harry Shipman, Annie Jump Cannon Professor of Astronomy, has won national recognition for both his research and his teaching. In May, Shipman received a prestigious National Science Foundation Director’s Award for Distinguished Teaching Scholars, the highest award presented to professors who excel at both undergraduate teaching and scholarship.

Q: Using a telescope, how much of the planet's surface could you see?

A: When I looked at Mars through the telescopes at Mt. Cuba Observatory recently, I saw about half of the planet. The south polar cap was pretty easy to see. Just at the limits of visibility was a good-sized dark area, produced by the shifting sands on Mars.

Q: Have there been any effects on the Earth due to Mars' closeness?

A: Nope. Unless you count the effects on people who suddenly seem to develop an interest in the red planet, given this close passage.

Q: Has Mars closer proximity to Earth helped scientists learn more
about it? If so, what?

A: The Hubble Space Telescope project has obtained a number of images of Mars, taking advantage of its comparatively close passage. These images, at [http://hubblesite.org/newscenter/archive/2003/22/] are really good, showing more detail than one normally gets.

Article by Barbara Garrison

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