Mars Probes On Crash Course

Two softball-size probes were literally sent on a collision course toward Mars in search of water and test technology that could revolutionize solar system exploration.

"We're not your average mission - we're slamming into a planet at 400 mph," said Deep Space Two project manager Sarah Gavit at NASA's Jet Propulsion Laboratory.

The hardy devices cruise along with the still-silent Mars Polar Lander. Unlike the lander, the probes' 77-mile fall is slowed by pricey parachutes or thrusters. They penetrate the planet like lawn darts.

Deep Space Two is risky; just ask anyone who has destroyed a laptop computer by dropping it. If successful, though, fleets of microprobes could be sent to study more planetary territory at less cost and risk than current spacecraft.

The $29.6 million Deep Space Two probes are part of NASA's New Millennium program, a series of inexpensive missions testing untried technology for future spacecraft. Ten systems were ready to be tried out during the Mars mission.

NASA's Deep Space Two probes will crash into the Martian surface.

For four years, Gavit and her team have been throwing models out of airplanes over the Mojave Desert and firing electronics out of air guns in Florida to find designs and materials that might survive the force of smashing into the surface.

After about 20 attempts, they finally arrived at a design that should withstand the force of impact, which will be 60,000 times stronger than gravity on Earth.

Each probe is protected from the heat of entry by a gray basketball-size aeroshell that shatters as it hits the surface. Most of the weight is located at one end of each unit to ensure stability, similar to badminton birdies and lawn darts.

Impact causes a silver, bullet-like penetrator to separate from the center of each probe and plunge up to two feet into the ground. A cable connects it to the orange aboveground unit holding an antenna and batteries.

Even with successful tests on Earth, there's no guarantee of survival on Mars. The eight-pound probes might hit rocks and shatter. The antennas could be swallowed up by soft dusty soil. A sudden gust of wind could blow them upside down during flight.

"We've got a pretty robust design, but it's like throwing one of these things out here in the middle of Pasadena and saying it has got to penetrate no matter where it lands," Gavit said. "If it lands in the middle of the freeway, it's not going to penetrate."

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