More than four decades ago, the Soviet Union dropped a heavily instrumented craft onto the Martian surface intact — only to have it fall silent seconds later. After a prolonged search, a group of Russian space enthusiasts think they've finally spotted it in NASA imagery.
By 1971, the United States had won the Moon Race handily, but interplanetary bragging rights were still very much up for grabs. That summer both the U.S. and U.S.S.R. launched pairs of spacecraft toward the Red Planet. NASA lost Mariner 8 during launch, but Mariner 9 slipped into orbit around Mars as planned and mapped most of its surface (once a globe-engulfing dust storm abated).
The Soviet craft, Mars 2 and 3, were more complex, each consisting of an orbiter and a heavily instrumented lander. Although the Mars 2 lander crashed during descent, its counterpart fared better. On December 2, 1971, Mars 3's lander thumped roughly onto the surface, opened its four petal-shaped covers, and began transmitting a panoramic TV image to its orbiter. But the signal stopped abruptly after just 14½ seconds — only part of a single, blank image reached Earth. To this day it's unclear whether the lander or the radio relay on the orbiter failed.
Now one aspect of this decades-old mystery might finally be resolved. The Mars 3 lander dropped into the broad crater Ptolemaeus at 45° S, 158° W, though its exact location has remained uncertain. However, the super-sharp HiRISE camera on NASA's Mars Reconnaissance Orbiter has imaged a set of objects on the surface that appear to be the lander, along with its heat shield, retrorocket, and parachute.
The identifications weren't made by NASA scientists but instead by a group of Russian space enthusiasts led by Vitaliy Egorov. Last November they painstakingly combed through a HiRISE image of the landing area taken in 2007, trying to match features with Egorov's computer-generated models of how the various pieces might appear from orbit. It wasn't an easy task: that single image contained 1.8 billion pixels, enough to fill about 2,500 computer screens.
"When I suggested that our group begin searches, 15 or 20 people responded," Egorov says. "We examined all of the picture but didn't find the lander — enthusiasm quickly died away." So he continued to pore over the image on his own, finally spotting the Mars 3 candidate last New Year's Eve. Egorov has a web page that details the group's search effort (auto-translated to English here). "I think of it as a gift from Santa Claus or the Russian Father Frost," he muses.
Egorov then contacted Alexander Basilevskiy, a planetary scientist at Moscow's Vernadskiy Institute who's been aiding the search effort, and Basilevskiy in turn got word to Alfred McEwen (University of Arizona), who leads the HiRISE team. A second image of the area was beamed back to Earth on March 10th.
All the right pieces seem to be there, though they're strewn over about 3 miles (4½ km) of terrain. "My biggest doubts are about the heat shield," Egorov admits. But he's confident about the other identifications, noting that there are "too many arguments in favor of a real find." The HiRISE images, whose individual pixels correspond to 10 inches (25 cm) on the Martian surface, even reveal a beefy, 15-foot-long chain that connected the retrorocket to the landing capsule.
"The candidate parachute is the most distinctive and unusual feature in the images," McEwen comments on the HiRISE website. "It is an especially bright spot for this region, about 7.5 meters in diameter. The parachute would have a diameter of about 11 meters if fully spread out over the surface, so this is consistent."
McEwen plans to take more close-ups of the presumed spacecraft parts, but those views are unlikely to reveal why the spacecraft's transmission failed so abruptly.
Still, nothing in the HiRISE images suggests that any kind of malfunction occurred, bolstering the long-held view of many space experts that Mars 3 — rather than Viking 1, which arrived five years later — should be credited with the first successful landing on Mars.