Md. scientists involved in 2 new space missions

NASA approves funding for closer looks at planet Mercury, comet

July 09, 1999|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

During the next 10 years, some Maryland scientists will be sending a spacecraft to the broiling planet Mercury, while others blast a comet with an 1,100-pound bullet.

NASA gave the green light this week to Messenger, a $286 million proposal to send a robotic spacecraft to orbit the planet Mercury in 2009.

The orbiter would be built and managed by the Johns Hopkins University's Applied Physics Laboratory, in Laurel.

The space agency has also approved Deep Impact, a $240 million project to study the composition of Comet P/Tempel 1.

University of Maryland scientists will send a spacecraft toward a July 4, 2005, encounter with the comet, then blast it with a high-speed copper projectile.

The Deep Impact mission would be led by Michael A'Hearn, of College Park.

The Maryland projects were proposed for funding under NASA's Discovery program -- a series of relatively low-cost, unmanned space science missions.

The two winners were chosen from 26 proposals submitted by institutions across the country.

"The mood here is euphoric, to say the least," said Max R. Peterson, APL's Messenger project manager.

Using improved technology

The mission will be the first to approach and study Mercury -- the planet closest to the sun -- since Mariner 10 was there in 1974 and 1975.

The Mariner fly-bys were brief encounters. Parts of the planet were never photographed, and the clarity of the pictures taken was well below today's standards.

"Their resolution was phenomenal for the time, but in the 20-odd years since, we've had unbelievable increases in resolution," Peterson said.

Messenger (for MErcury Surface, Space ENvironment, GEochemistry and Ranging Mission) will be launched in spring 2004.

After two energy boosts from the gravity of Venus, it will fly by Mercury twice in 2008. It will begin orbiting in September 2009.

During a yearlong visit there, the spacecraft will map the entire planet; study its geology, space environment and magnetic field; and search for water ice in its polar craters.

The data should provide new understanding of how the solar system's four rocky planets -- which include Earth -- were formed and evolved.

Among the engineering challenges, Peterson said, will be protecting the spacecraft's instruments from searing solar heat and radiation.

The planet is just 36 million miles from the sun, compared with Earth's 93 million miles. Its surface temperature averages 333 degrees Fahrenheit.

APL engineers hope to shield Messenger's instruments enough to provide them with a room-temperature operating environment.

Messenger is being led by principal investigator Sean C. Solomon, of the Carnegie Institution of Washington.

Peterson said about half the $286 million that NASA has allocated for the work will be spent in Maryland.

Maryland won't see nearly that much money from the $240 million Deep Impact project.

Although it is being led by A'Hearn and a handful of scientists at College Park, the mission will be managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The craft itself will be built by Ball Aerospace, in Boulder, Colo.

News that NASA selected Deep Impact for funding this year sparked excitement at College Park, however.

"I broke out in goose bumps," said Lucy McFadden, a member of the project's science team.

Long trip for one shot

The spacecraft will be launched in January 2004 and fly toward a July 4, 2005, meeting with P/Tempel 1. Once in range, it will fire an 1,100-pound copper projectile.

The big bullet will strike the 4-mile-wide comet at about 22,300 mph, delivering an enormous punch.

Depending on the density of the comet's icy core, the blast could open a crater big enough to hold a seven-story building, or pass right through and out the other side.

The blast should throw out enough material to be visible to amateur astronomers, and mission planners hope to provide video images, from the spacecraft, in near-real time.

"It's a little bit aggressive," McFadden said. But "we don't expect to blow it to smithereens."

Scientists do hope to blast enough of the comet's interior material into the open to analyze its chemistry.

Their goal is to compare the comet's insides with the material that routinely boils off the surface as it nears the sun.

Testing assumptions

Astronomers have always studied that surface material with the assumption that it was representative of the entire comet, and that comets have remained unchanged since the solar system was formed 4 1/2 billion years ago.

If those things were true, their analyses would reveal something about the contents and conditions in the early solar system.

But some scientists have suggested that comets might have encountered enough heat during their lifetimes to produce chemical changes on the surface.

With Deep Impact, they will get an opportunity to compare a comet's insides with its exterior and run an important check on their assumptions.

"If the interior is different, we're going to have to make corrections," McFadden said.

Two other proposed Discovery missions with Maryland ties were not selected in the final round of NASA funding this year.

They were a mission to Mars' moons that APL was to have managed and an orbital mission to Venus led by a scientist at NASA's Goddard Space Flight Center in Greenbelt.

Pub Date: 7/09/99

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