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A close encounter with Mars

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A close encounter with Mars

The Red Planet makes its nearest approach to Earth in 1999 this week and next

Once in about every fifteen years a startling visitant makes his appearance upon our midnight skies,--a great red star that ... mounting higher with the deepening night, blazes forth against the dark background of space with a splendor that outshines Sirius and rivals the giant Jupiter himself. -- from Mars by Percival Lowell (1895)

HST image of MarsApr. 23, 1999: Go outside about 2 hours after sunset and look toward the East. That brilliant red star you see just above the horizon is Mars, and it's headed our way.

There's nothing to worry about. Mars won't come any closer to Earth than about 54 million miles, but this week and next Mars will be brighter and nearer to Earth than at any time since 1990. It's a great opportunity for amateurs to see details on the red planet through a small telescope or to simply view Mars with the naked eye.

Right: This NASA Hubble Space Telescope view of the planet Mars is the clearest picture ever taken from Earth, surpassed only by close-up shots sent back by visiting space probes. The picture was taken on February 25, 1995, when Mars was at a distance of approximately 65 million miles from Earth. The Red Planet will be even closer to Earth during the coming weeks. more information

Mars at opposition On April 24, Mars reaches "opposition," which means that it passes through a point in its orbit that is directly opposite the sun as seen from Earth. At opposition Mars rises near sunset and is visible all night from most latitudes. Shining at magnitude -1.6, it will appear to be one of the brightest stars in the sky on Saturday night. In fact, it will be as bright as Sirius and second only to Venus in brilliance.

"This is a great time to view Mars with the naked eye," says Dr. John Horack, a NASA astronomer. "By mid- to late-June the planet will be a full magnitude dimmer, but for the next few weeks it will be spectacular."

To find Mars simply go outside any night for the next couple of weeks about an hour or two after sunset. Reddish colored Mars should be easy to spot 20 to 25 degrees above the horizon in the east-southeast. Later in the evening, near midnight, Mars can be seen due South about 45 degrees above the horizon from mid-latitude sites in the northern hemisphere.

the planet Mars in Virgo on April 24 1999Left: On April 24, 1999 when Mars reaches opposition, the planet can be found in the constellation Virgo about 15 degrees East of the blue-white star Spica (magnitude 1.2). This image shows Mars and Virgo viewed about 40 degrees above the southern horizon at 11:30 p.m. local time on April 24.

If the orbits of Mars and Earth were perfectly circular then the two planets would be closest together on April 24 at the exact moment of opposition. But that's not the case. Both planets follow slightly elliptical paths around the Sun, so the instant of closest approach doesn't arrive until May 1st when Mars will pass within 54 million miles of Earth.

Duane Hilton strikes again By that time Mars will be slightly dimmer than it was on April 24, but it will appear to be bigger -- nearly 16 arcseconds across. That's large enough to reveal details like the north polar cap, dark surface markings and clouds to amateurs viewing the planet through a 6- to 8-inch telescope. Sky & Telescope has prepared an excellent Mars Observing Guide which reviews what can likely be seen on the red planet through a telescope this month.

Martian oppositions occur about once every 26 months, but due to the elliptical shape of planetary orbits not all oppositions are the same. This year the apparent diameter of Mars will reach 16 arcseconds, the largest it's been in years, but in 2003 the disk will be a whopping 25 arcseconds across! That's the maximum size Mars can ever be as seen from Earth.

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Experts note that bigger is not always better. During some of the most anticipated oppositions, such as in 1956, dust storms on Mars have obscured features from view. On the other hand, good Martian weather can lead to crystal clear viewing conditions when the disk is smaller. The Martian atmosphere was especially transparent at opposition in February 1995 when the disk was only 13.6 arcseconds across. Both amateurs and professionals captured unexpectedly crisp views of the red planet during that apparition.

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Of course the clearest view of Mars this week will be from the vantage point of NASA's Mars Global Surveyor (MGS) spacecraft, orbiting just 235 miles above the planet's surface. Global Surveyor, which reached its final orbit in February, continues to relay stunning images of ancient Martian volcanoes, canyons, impact craters, and much more. While images from the MGS are unmatched for their coverage and resolution, it's hard to beat a glimpse of the Red Planet at opposition, twinkling among the stars on a clear spring night.

As Percival Lowell noted in his classic book Mars (1895), "no other heavenly body, Venus and the Moon alone excepted, ever approaches us so near..." and although the red planet "is neither new nor intrinsically great, he possesses for us an interest out of all proportion to his size or his relative importance in the universe." Lowell felt the enchantment of Mars to such a degree that he devoted his fortune and the latter part of his life to the study of its mysteries. Was it worth it? Is the allure of Mars really so powerful? For the next two weeks you can see for yourself.

Above: Zooming in on Mars. A. A Hubble Space Telescope View of Mars from 65 million miles distance; B. A Martian volcano, Apollinaris Patera, with white clouds near the summit photographed from above by Mars Global Surveyor; C The rock "Barnacle Bill" as seen from a distance of a few meters at the Mars Pathfinder landing site; D: Possibly the closest-ever view of Mars. This high-resolution electron microscope image shows an unusual tube-like form less than 1/100th the width of a human hair. It was found in meteorite ALH84001, believed to be of Martian origin and is thought by some scientists to be evidence of ancient Martian life. more information. Web Links

The Planet Mars - from the SEDS Nine Planets web site

Life on Mars - A review of evidence of signs of life in the Allen Hills meteorite

Mars Global Surveyor - home page

Mars at opposition - 1995 images from the Hubble Space Telescope

Mars - by Percival Lowell, 1895

Related Stories:

Summer snow on Mars -- New Mars Global Surveyor images reveal snowy slopes. Mar. 25, 1999 NASA NASA Science News

A new face on Mars has scientists smiling -- MGS beams back pictures of the "Happy Face Crater". Mar. 12, 1999 NASA NASA Science News

Mars mapping begins in earnest -- MGS achieves its final orbit. Mar. 12, 1999 NASA NASA Science News

A steamy cover-up on the red planet -- New evidence for active volcanism on Mars. Feb. 18, 1999 NASA NASA Science News

The Sands of Mars -- Oct. 29, 1998 NASA NASA Science News

New NASA images of the Martian North Pole -- Oct. 23, 1998 NASA NASA Science News

New images of volcanoes on Mars and Io -- Oct. 14, 1998 NASA NASA Science News


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For more information, please contact:
Dr. John M. Horack , Director of Science Communications
Author: Dr. Tony Phillips
Curator: Bryan Walls
NASA Official: John M. Horack