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NASA Launches Mercury Probe

Posted on: Wednesday, 4 August 2004, 06:00 CDT

NASA launched the Messenger spacecraft on the first mission in 30 years to the planet Mercury as astronomers continue to search for the origin of Earth.

Scientists hope the seven-year journey to the planet will end in a better understanding of the formation of Earth, Venus and Mars and their interactions with the sun. The first look at the planet came from the Mariner 10 voyage, which mapped about 45 percent of the planet.

"We don't know what the rest of the planet looks like," Rob Gold, the mission's payload manager, said in a telephone interview. "The part that they did see looked rather cratered like the moon, but what geological history, what information it tells about the formation of the solar system and about how the planets evolved -- that's all still a mystery."

The robotic Messenger program comes as NASA works to implement President George W. Bush's $12 billion plan for human missions to the moon and Mars as steps towards further exploration of the solar system.

The $286 million, 2,442-pound satellite was launched at about 2:15 a.m. local time aboard a Boeing Co. Delta II rocket from the Cape Canaveral Air Force Station in Florida. It's the first mission to Mercury since Mariner 10 visited in 1974 and 1975. The lift-off was delayed yesterday by weather.

Last year's destruction of the space shuttle Columbia NASA grounded human space flight, leaving NASA to focus on robotic missions. In addition to Messenger, NASA has a satellite orbiting Saturn and a pair of robotic geologists roaming Mars.

Messenger, powered by two solar panels and a nickel-hydrogen battery, will fly 4.9 billion miles, passing Earth and Venus before it arrives at Mercury in January 2008. It will move past the planet three times and then enter orbit in March 2011.

Mercury is about 3,000 miles wide, more than half the size of Earth, and at a distance of 36 million miles, the closest planet to the sun.

The spacecraft will orbit about 124 miles above Mercury at its lowest point, using seven scientific instruments to determine the composition of rocks on the surface, measure the thickness of the planet's crust and examine the magnetic field and polar regions.

Radar images of the poles have shown "bright" areas that may be ice in craters, and scientists believe there are areas that get cold enough for ice to form -- a possible sign the planet may have once been able to support life despite the fact that its sunny side is as warm as 900 degrees Fahrenheit and its dark side is as cold as -300 degrees Fahrenheit.

"Life as we know it would have an awfully hard time surviving on Mercury because of the very high temperature extremes," Gold said. "But finding water on a planet that close to the sun that had such an extreme history would be quite a surprise."

The spacecraft was built by Johns Hopkins University's Applied Physics Laboratory in Laurel, Md., which also operates Messenger. Its instruments were built by the laboratory, NASA's Goddard Space Flight Center, the University of Colorado and the University of Michigan.

Alliant Techsystems Inc.'s Composite Optics unit provided the structure, GenCorp Inc.'s Aerojet division built the propulsion system and closely held KinetX Inc. provided the navigation system.

Messenger stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging. It's the seventh spacecraft in NASA's Discovery program, which includes the 1997 Mars Pathfinder mission and Stardust, which collected a sample from a comet earlier this year.

The European Space Agency and the Institute of Space and Astronautical Science in Japan plan to launch two spacecraft on a joint mission to study Mercury in 2011.

Contributing: Alex Morales.

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