NASA loses Mars Climate Orbiter.

Mars has swallowed another spacecraft.

NASA's Mars Climate Orbiter, intended as the Red Planet's first weather satellite, appears to have burned up or been torn apart just as it entered Martian orbit on Sept. 23. The satellite was to have served as a radio relay for its sister craft, Mars Polar Lander, expected to touch down on Dec. 3.

An unexplained navigation error sent the $125 million Orbiter about 100 kilometers lower than planned into the Martian atmosphere. At that altitude, only about 57 km above the planet's surface, mechanical stresses and heat from atmospheric friction would have destroyed it, says project scientist Richard W. Zurek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Scientists calculate that the craft could not have survived at any altitude lower than 85 km.

Over the past 2 decades, several Mars-bound Russian and U.S. spacecraft have perished, notably NASA's $1 billion Mars Observer (SN: 8/28/93, p. 134). Ironically, Mars Climate Orbiter carried a duplicate of one of Observer's instruments, an infrared radiometer designed to measure the distribution of temperature, pressure, dust, and water vapor in the Martian atmosphere.

The craft would have broadcast daily weather images and data for an entire Martian year--687 days. Gathering that information could now be delayed for a decade, because Mars missions for the next several years have a different agenda: to collect samples from the Red Planet and bring them to Earth (SN: 4/25/98, p. 265).

Of more immediate concern is that the Mars Polar Lander, which will dig about a meter into Martian ice and dust near the south pole to look for evidence of recent climate changes, will have to rely on other means to communicate with Earth. Zurek says that Lander will likely use Mars Global Surveyor, which has orbited the Red Planet since 1997, to relay much of its data. That will reduce the time that Surveyor has to conduct its own mission, imaging the planet and mapping Mars' gravity.

Alternatively, Lander can communicate directly with Earth but so slowly that it couldn't broadcast all its planned observations. Zurek adds that it's unclear whether Lander, powered by the limited sunlight near the south pole, will have enough energy to send signals to Earth and carry out its full complement of Martian studies.

For the first few days of Lander's 3-month mission, the craft may have no other way to communicate. During that time, Surveyor's relay link is likely to be occupied by two small probes that have hitched a ride on Lander and will independently punch into the Martian soil.

Several space-policy analysts told SCIENCE NEWS that the loss of Mars Climate Orbiter, as well as two other NASA setbacks--the degradation of detectors on the Chandra X-ray Observatory and wiring problems on the space shuttle--don't seem to have altered the debate over the agency's budget. The House has proposed to cut $1 billion from the agency's appropriation for next year, but a Senate proposal would fund the agency at the current level.