Its cold on Mars

THE Mars Pathfinder may have lost its way on the red planet. Scientists at the US National Aeronautics and Space Administration’s (NASA’s) Jet Propulsion Laboratory (JPL) at Pasadena, California, have virtually given up hope of reviving the probe. Both the Pathfinder lander and its 10-kg rover, the Sojourner, have been mired in technical problems for the last two months. But scientists are not disappointed by this. They point out that the mission survived thrice longer than the 30 days it was expected to go on, after it made a much publicised landing on July 4. The last that was heard from the rover was on October 7. Freezing in the -50°C temperature of the Martian desert, the foot-long rover is now lost in an alien world, desperately sending signals to home base and not receiving any response. The last time JPL scientists established contact with the Pathfinder was for 15 minutes on September 27. The rover, meanwhile, continues to follow a preprogrammed path around the lander. More important than the present setbacks, however, is what has been achieved by the mission, especially in comparison to the Viking missions of 1976. The Pathfinder mission is a vast improvement on the Viking missions. For one, the Pathfinder is far cheaper than the Viking missions. In keeping with NASA’s policy of cutting down costs, the Pathfinder project is estimated to have cost US $266 million. This is a vast improvement on the Viking missions that had a price tag of US $3 billion. The Pathfinder also saved a lot on fuel by using a landing system featuring inflatable airbags. And the data and pictures sent by the Pathfinder are far superior to those returned by the Viking missions. It has sent back some 16,000 photographs that has fascinated the scientific community of the world no ends. The Sojourner roamed hundreds of metres across the Martian surface, proving that robot technology will be useful for future missions. And the data sent back by the mission has got scientists working overtime to improve our understanding of Mars.

Contact has been lost
with both the lander
and the rover. But
the data and
photographs sent
back are invaluable

What came out

When the Pathfinder opened its bewildered eyes to peer upon the Martian landscape, humans had missed out on life on Mars — if it ever existed — perhaps by millions of years. There were signs of mechanisms that supported life but had ceased to function. For a short time in Martian history, an Earth-like world might have existed. The lander sent back spectacular pictures of a rocky plain near the mouth of a channel called Ares Vallis that is thought to have been carved out by running water some three to four billion years ago. According to geologists, the deluge may have released 100 million cubic metres of water per second. But the oceans of Mars do not exist today. Visible evidence that the planet was once warmer with an atmosphere thick enough to prevent water from boiling off is available in the form of ancient winding river valley beds, shorelines and flood plains. Rounded pebbles shaped by the water bear testimony to Mars’ extravagant youth. But something ripped the atmosphere off the planet. The water that once flowed across its surface vanished, leaving behind a glorious desert and a denuded landscape. How did Mars live and how did it die? Is there a lesson for us in this? Will the processes that sapped life from Mars affect the Earth one day? Did the very atmosphere — the stuff on which life subsists — kill Mars? One possibility is that Mars may be trapped in a self perpetuating ice-age — its atmosphere trapped as

The Surveyor
mission will answer
a crucial question.
What is the
composition of the
planet’s core?

permafrost in its polar regions. What remains of the Martian atmosphere is composed mainly of carbon dioxide. A thick coat of a greenhouse gas such as carbon dioxide would have been needed by Mars to keep it warm enough for water to flow on its surface. However, most of this carbon dioxide could have reacted with Martian rock silicate to form carbonates. The Martian landscape could have acted as a giant sponge sucking away the atmosphere till it finally became too thin to sustain waterbodies or life. Earth lifeforms mimic this process in a different manner. Plants strip carbon dioxide from the atmosphere during the process of photosynthesis. The shells of dead sea creatures end up as carbonates or chalk. But the Earth has a high degree of volcanic activity. This volcanic activity maintains the status quo by pumping carbon dioxide back into the atmosphere. Therefore the levels of carbon dioxide remain fairly constant. Meanwhile, the Pathfinder has yielded the strongest evidence possible that Mars may have supported life. Like the Earth, Mars has a crust, a mantle and an iron core. That Mars may not be composed of solid rock came to light after measuring the changes in radio signals from the Pathfinder. Scientists were able to infer the composition of the interior of the red planet by comparing these signals to the ones sent out by the Viking spacecraft. William Folkner, one of the scientists at the JPL, said that while Mars had an iron core, they did not know whether it was molten or solid. Molten cores are normally rare, with only Earth and Mercury being known to have them. The motion of the molten core acts like a dynamo and creates Earth’s magnetic field. Though it cannot be established that Mars has a molten core, the fact that the planet had sufficient heat to create the layers of a crust, a mantle and an iron core shows that it was warm and wet enough to be able to support life. The first rock studied by the rover, nicknamed Barnacle Bill, has turned out to be surprisingly rich in quartz. This could mean that the rock is of volcanic origin. If the estimates of scientists are anything to go by, Bill will go a long way in proving that the core of Mars has undergone a lengthy and varied melting, cooling and remelting.

The findings of the
Mars Surveyor will
simply rewrite all
the reference books,
says the project
manager

The Global Mars Surveyor

The Pathfinder and the rover are not the only explorers from the Earth to the red world. After a journey of 10 months and about 700 million km, NASA’s Mars Global Surveyor successfully eased into a wide orbit of about 300 km over the north pole of the red planet on September 7. The Surveyor came to life on September 10 when its engines functioned for 22 minutes, cutting down its speed to let it be captured by Mars’ gravity. The craft will map the planet’s surface for a Martian year, which is equivalent to about two Earth years. The significance of this can hardly be exaggerated. The last attempt to map Mars in 1993 failed when the Mars Observer went on the blink three days before it could reach orbit. This happened due a temperature imbalance in the fuel lines that caused a leakage, leading to an explosion that knocked out the radio. The Surveyor is expected to generate as much data as all previous missions to Mars put together. “It will simply rewrite all the reference books,” said Glenn E Cunningham, project manager of the Surveyor at the JPL. “We are just drained from the emotion of this accomplishment,” said Tom Thorpe, science manager for the Surveyor at the JPL. The Surveyor will start sending photographs in March 1998. These will be ten times better than those sent by the Viking orbiters. All future explorations of Mars will depend upon the findings of the Surveyor. The craft is equipped with a camera, a laser to measure the heights and depths of hills and valleys, and a spectrometer to determine the composition of the planet’s surface. In order to keep the costs of the project within the US $247- million budget, a technique known as aerobraking is being employed. Under this, the Surveyor will brake against the thin Martian atmosphere once on each orbit to slow down to its final orbiting speed, obviating the use of money and fuel-hungry thrusters. The lowest point of the Surveyor’s aerobraking orbit has been raised temporarily and aerobraking suspended while the flight team is analysing data to understand why one of the spacecraft’s two solar panels, which did not deploy fully, moved unexpectedly during a recent dip through the upper Martian atmosphere. The spacecraft’s current 35-hour orbit around Mars, which was taking it down to 121 km above the Martian surface during each of its closest passes over the planet, was raised to 170 km. This was done on October 12 by the operations team at the JPL and Lockheed Martin of Denver, Colorado, by per-forming a brief, 2.3-metre-per-second (about 8.3 km per hour) propulsive burn at the farthest point of the craft’s orbit around Mars. The panel’s performance has had no effect on the craft’s power. “We’re taking a break from aerobraking for the next few weeks while we study data to try to model and understand the apparent deflection of the solar panel that never fully deployed and latched in place after launch,” said Cunningham. “This delay in the aerobraking process will probably change the spacecraft’s final mapping orbit from the originally planned 2 pm passage over the planet’s equator in local Mars time to another time, and we are studying several other orbits that will give us nearly the same outstanding results.” Several other mapping orbits are available to the Surveyor to carry out its science objectives. The flight team will explore alternatives in the next few weeks to accomplish the lowest orbit possible and achieve a “sun synchronous” orbit. This will allow the Surveyor to fly over the Martian equator at the same local solar time in each orbit. These sun synchronous orbits have been planned in such a way that the spacecraft’s instruments always observe Mars at the same lighting angle during every pass over the surface. Preliminary data from the panel indicate that it has moved past what would have been its fully deployed and latched position, Cunningham said. In addition, the panel has shown some movement, rather than maintaining its rigid position during aerobraking. These changes occurred during the spacecraft’s fifteenth closest approach over the Martian surface on October 6, when the density of the Martian atmosphere doubled unexpectedly. “As we step back from aggressive aerobraking temporarily, we will have the opportunity to study the situation until we fully understand it,” Cunningham said. “We will take advantage of this opportunity to return some spectacular data from the camera and laser altimeter. The thermal emission spectrometer and magnetometer/electron reflectometer also will continue to collect data while we remain in this holding position.” These might help in clarifying one of the most intriguing aspects of Mars — the composition of its core. If Mars does have a molten core, the Surveyor would detect the magnetic field generated by it. If not, it would mean another round of hectic investigations for scientists. Scientists and observers around the world, in the meantime, will wait with bated breath for the results. The Earth’s relations with its solar cousin have never been so intense. And this will also be the most fruitful round of pleasantries, with a bright future for better a understanding.