Sunset over Mars

Requiem for the Mars Global Surveyor

By Stephen Ornes|Wednesday, March 14, 2007
Landmark discoveries of the Surveyor include a detailed topographical map of Mars (top), and deposits of the water-related mineral hematite (below).

When the Mars Global Surveyor left Earth in 1996, engineers gave the $220 million spacecraft a life expectancy of about one Martian year, or 687 Earth days. That was just enough time to map the Martian surface, take a few measurements, and fade away somewhere over Valles Marineris (Mars’s supersize answer to the Grand Canyon). Not bad for a contraption that looked like the top of a beheaded windmill.

In fact, the surveyor soldiered on for 10 years with barely a scratch. Then its processors somehow misfired last November, executing a fatal set of commands. Project manager Tom Thorpe says the error might have caused the spacecraft to expose a sensitive panel to the sun. “It probably fried the battery,” he says. The surveyor vanished behind a Martian eclipse, and NASA’s messages to the spacecraft went unanswered. There is still an outside chance that NASA will hear from Surveyor again, but it is slim.

Debuting shortly after the 1993 demise of the Mars Global Observer, which went dark just as it approached Mars’s orbit, the Global Surveyor represented a triumphant return to Martian science for NASA. Not only was Surveyor smaller and cheaper, it also sent more data back to Earth than all previous Mars missions combined and produced the first topological map of the planet. The surveyor’s magnetic field studies suggest Mars used to have a surprisingly Earth-like churning dynamo core. Late last year, a new set of photos revealed scars from fresh meteor impacts; others showed mineral deposits in gullies that suggest water still flows on the Red Planet. Over its 10-year life span, the spacecraft observed the Martian surface and atmosphere repeatedly, exposing details—like the shrinking carbon dioxide ice cap on the south pole—that would have been lost to onetime measurements. “It gave us the information to go from looking at Mars as a whole planet, with having telescopic views of it, to understanding it regionally,” says Michael Meyer, NASA’s lead scientist for the Mars Exploration Program.

Images from the Surveyor (clockwise from upper left): an illustration of the satellite, the structure of the carbon dioxide ice cap at the planet's south pole, riverbed surface patterns consistent with flowing liquid, and abundant impact craters on Mars' surface, many of them weirdly reshaped by weathering.
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