Soviet Mission: Mars
LOSS of contact with the Phobos 2 spacecraft when it was studying that martian moon last March was a great disappointment for Soviet - and world - science. But it's a mistake to continue to consider the twin spacecraft mission only in the light of that failure. It pioneered new types of Mars study and returned data whose value is becoming evident. The Soviets say they will learn from the mistakes and carry on. We should take them seriously. They had failures at Venus, too. In the end, they succeeded brilliantly. Their craft even returned data from the sizzling (455 degrees C) surface. Vassily Moroz of the USSR Academy of Sciences' Institute of Space Research noted during a recent United States visit that the Soviets sent 15 spacecraft to Venus over 20 years. Now, he said, ``We have decided that our next beloved planet will be Mars.''
The limited success of the aborted Phobos mission shows what the Soviets can do - especially when they draw on outside strength. The project had 15 international partners, including the European Space Agency. The Phobos 1 and 2 spacecraft were equipped to study Mars, the sun, and the interplanetary medium, as well as the moon Phobos.
Yuri Zaitsev, who heads the academy institute, detailed the data harvest recently in New Scientist. He says that Phobos 1, launched in July 1988, returned 140 ``high quality'' photos of the sun, and other important solar data before operator-error disoriented the craft. Phobos 2 made even more extensive solar and interplanetary measurements.
The Mars data include the first detailed infrared images of the planet - images that literally picture the surface by its heat emission rather than by reflected sunlight. They cover an equatorial band about 1,500 kilometers (932 miles) wide showing details as small as 2 km across. Other instruments recorded emissions at many wavelengths that should help in analyzing mineral composition of some surface rocks. A profile taken through the atmosphere records the distribution of various gases with height.
Intriguing data that show the interplay of magnetic fields and particles around Mars suggest how the planet loses its atmosphere to space. Electrically charged gas particles in the upper atmosphere leak away along magnetic channels. Mars' atmosphere is losing between 1 and 2 kilograms (2 to 5 pounds) of its substance a second. At that rate, Zaitsev says, Mars could lose its atmosphere in a time much shorter than the age of the solar system.
At Phobos, the craft took 40 TV images from distances between 200 and 400 kilometers, showing details down to 40 meters (131.25 feet) across during its closest approaches. These and other data have enhanced knowledge of this moon even though the craft lost radio contact on March 27 before it could close in and land instruments. The new data tend to confirm speculation that this dark moon (4 percent reflectivity) is similar to carbonaceous chondrite meteorites. Its surface temperature was about 27 degrees C. Gravitational interaction between spacecraft and moon will help scientists pin down the moon's mass, density, and internal structure.
The Soviets have shown the potential for advanced martian research. Their next challenge will likely be a 1994 mission, now awaiting final approval. It would include surface probes and instrumented balloons as well as a Mars orbiter. If Soviet space scientists become as successful at Mars as they have been at Venus, they will open valuable opportunities for international collaboration, including US-USSR cooperation. Let's wish them well.