Tonight's sky will offer 'close-up' look at Mars

November 19, 1990|By Frank D. Roylance | Frank D. Roylance,Evening Sun Staff

With war looming in the Persian Gulf, it may seem ominous that the planet Mars -- named for the Roman god of war -- looms bigger and brighter in the nighttime sky this month than any other object except the moon.

But it's no omen, astronomers say, just the mechanical spinning of the solar system. And star gazers wielding everything from binoculars to the Hubble Space Telescope are drawing a bead on Mars for their last best view of the Red Planet in this century.

Tonight, the Earth makes its closest pass by Mars until the year 2001, coming within 47.4 million miles of Mars as we pass between it and the sun.

This encounter isn't the closest in recent years. We came within 36 million miles during the last such event, in September 1988.

But compared with its average distance of 141 million miles from Earth, Mars is very close, indeed.

It's a chance for astronomers -- amateur and professional alike -- to try for a good look at the only planet in the solar system whose surface can be seen in any detail from Earth.

"It's very beautiful," said Herman Heyn, Baltimore's "street astronomer."

Since last December, Mars' brightness has increased 20-fold as Earth has approached and the Red Planet's apparent size has more than quadrupled.

"I think a lot of people are probably noticing it on their own without realizing what they're looking at," Heyn said.

With Earth now in a straight line between the sun and Mars (called "opposition"), the Red Planet is rising in the east just as the sun is setting in the west. By midnight, it's directly overhead.

With the naked eye, or binoculars, Mars looks like a very bright, reddish-orange star.

Mike Hall, an amateur astronomer in Relay, has been watching Mars through a 12 1/2 -inch reflector telescope on his back porch.

"I've been able to see some dark markings on it," he said, despite the glare of lights of nearby Baltimore.

"With some special filters, some people have been able to see clouds near where morning horizon is," Hall said. "It's also fairly easy to see the polar caps."

Heyn, who often makes his telescope available to pedestrians in Fells Point, said he's been avoiding Mars. At barely twice the size of our moon, and 205 times more distant, he said, Mars can be disappointing.

"To me, and for most people -- even for most amateur astronomers -- Mars is probably more beautiful to look at than it is interesting," he said.

"To really get some detail, you've got to have great atmosphere and the right filters . . . and also a superb telescope, the bigger the better," Heyn said.

Nevertheless, he said, amateurs will be out there trying.

"They'll be looking . . . and wondering whether there's something wrong with their telescope," Heyn said. "I do, and I feel like I want to kick it."

To star-gazers using only their naked eyes or binoculars, however, Mars is "a very pretty sight, because it's close by another bright star, Aldebaran, in the constellation Taurus," Heyn said. "Aldebaran also happens to be a kind of reddish color, and it's a beautiful pairing of two reddish objects."

"If you're looking at Mars, go a little to the right and you'll bump into this cluster of stars [called the Hyades] that is quite breathtaking with binoculars," he said.

"Another great binocular sight in that same area is just above Mars. It's called the Pleiades, the Seven Sisters. Even with small binoculars, rather than six or seven stars, you'll see 50 or 100."

Astronomers at the Space Telescope Science Institute are especially excited about this first close encounter with Mars since Hubble was launched last April. They are now programming Hubble's Wide Field/Planetary Camera for a look at Mars next month.

Originally timed to coincide with this month's opposition, the observations were delayed by tests ordered after flaws were discovered in the telescope's mirror.

Hubble planning scientist Marc Buie said a team led by University of Toledo astronomer Philip B. James will take three sets of seven photographs of Mars Dec. 13 and 14, in wavelengths from the ultraviolet to the infrared.

"The three sets taken together will cover the entire surface of Mars that can be seen from Earth," Buie said, about 90 to 95 percent.

"They're trying to get a global picture of Mars. You can't do it from a single observatory on the ground . . . because Mars rotates once for every time the Earth rotates, so every night . . . you're going to see same face of Mars."

Buie said Hubble may not be able to see such detail as Mars' huge volcanoes and canyons. But the photographs in various wavelengths will allow James to map rock types and minerals across the Martian surface, and analyze their recent geological history.

Scientists also hope to use measurements of atmospheric ozone on Mars to deduce the amount of water on the planet's surface, Buie said.

And if they get lucky, they also hope to study the development of dust storms, which are common on Mars at this time in its year.

Further Mars observations are planned in 1991, as Earth pulls rapidly away from the Red Planet. Buie said it's the first phase of a three-year Hubble study of Mars.

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