For a brief time last week, there was a small flutter that raised the tantalizing possibility of scientists coming closer to using the L word regarding the exploration of Mars.

Alas, as a corollary to the famous comment by Mark Twain, reports of life on the red planet have been exaggerated.

The reference originated in a story published by BBC News Online on July 15, which stated the European Space Agency's Mars Express orbiter had detected the presence of ammonia in the planet's atmosphere.

According to the story, scientists at the European Space Agency said the Mars Express spacecraft's instruments had acquired the chemical signature of ammonia, which could survive for only a short time in the cold, dry Martian atmosphere without dissipating completely. Therefore, the gas must be replenished somehow, they said, adding that the only two possible sources were active volcanoes -- none of which have been found yet on Mars -- or microbial action.

The story also said Vittorio Formisano, principal investigator for the instrument, was expected to release details of new findings at an international conference being held this week in Paris.

Although Mars Express has been in orbit around Mars since December 2003, scientists have analyzed only a fraction of the data, so it may yet yield the discovery of ammonia. But as of right now, there is no confirmation.

The detection of ammonia would be a powerful indication of life on the red planet, perhaps the most powerful indication, short of discovering microbes or plant life directly.

Mars Express has provided the strongest hint so far of life on Mars, however, when its instruments detected -- and ground-based observations confirmed -- methane in the planet's atmosphere last March.

Methane is a colorless, odorless gas that is common on Earth. For example, it is the principal ingredient of natural gas. It also occurs, in a dangerous, potentially deadly way, in coal mines, and it is the product of a process called anaerobic decomposition, in which bacteria in the ground, underwater, and even in the digestive systems of certain animals -- such as cows -- essentially digest the remains of plants and animals.

The only other natural process that can release methane into the atmosphere is volcanic activity, either eruptions or slow disbursement of the gas via hydrothermal vents -- which on Mars seems entirely plausible because NASA's Opportunity rover earlier this year found that water once flowed on the surface.

Whatever the source, however, on Mars, with its thin atmosphere and low gravity, methane could not remain long. Within a few hundred years, any amount would disappear, forming water vapor and carbon dioxide. So for methane to be discovered on Mars, it must have a source that is remanufacturing it.

The Mars Express, using an instrument called the Planetary Fourier Spectrometer, detected a tiny amount of the gas in the atmosphere -- about 10 parts per billion -- among the 95 percent CO2, and 5 percent oxygen, water vapor, carbon monoxide and formaldehyde.

Two other scientists, Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md., and Vladimir Krasnopolosky of Catholic University in Washington, detected the gas using ground-based spectroscopy.

Methanogens, the organisms on Earth that produce methane, break down organic tissue and release hydrogen and carbon -- methane's components. Methanogens do not need oxygen to live, so they could live beneath the Martian surface.

By finding traces of methane in the planet's atmosphere, the Mars Express orbiter and the terrestrial spectrometers have raised the distinct possibility the red planet harbors a rudimentary form of life. Unless scientists discover something new in the Mars Express data, however, methane -- and the signs of past water activity -- remain the only evidence suggesting such a possibility.

Meanwhile, NASA has extended the missions of its twin Mars exploration rovers -- Spirit and Opportunity -- for another seven months.

Firouz Naderi, director of solar system exploration at the agency's Jet Propulsion Laboratory in Pasadena, Calif., said he had recommended that the missions be extended.

Spirit and Opportunity, which landed on Jan. 3 and 23, respectively, were supposed to operate only for 90 Martian days. Then, based on the successful performance of both robotic craft, NASA in April decided to extend their missions until September.

Now, the rovers could be operating until February 2005 -- although to do so the mission staff will have to perform some creative financing and, eventually, they will have to create a virtual control center from their home institutions to save money.

Another challenge for both rovers is the approach of the Martian winter, which peaks in mid-September.

Dwindling daily sunshine means the rovers will have less solar power and take longer to recharge. Periods of rest and deep sleep -- as scientists call the power-conservation cycle -- will allow the rovers to keep working through the winter at lower activity levels.

Orienting the rovers' solar panels toward the north also will help boost power levels.

The rovers might work a little bit more every day, or a little bit more every other day, said Jim Erickson, project manager for the Mars Exploration Rover mission at JPL. We will see how things go and remain flexible.

Right now, Opportunity continues to inch deeper into the stadium-sized crater called Endurance, located in the equatorial area called Meridiani Planum.

On the other side of the planet, Spirit has found an intriguing patch of rock outcrop while preparing to climb up the Columbia Hills -- backward, however, to accommodate the rover's ailing front wheel.

In all, Spirit has covered more than 2.2 miles (3.5 kilometers) and has traveled six times its designed capacity. Its right front wheel has been experiencing increased resistance and recent efforts to solve the problem by redistributing the wheel's lubricant through rest and heating have been only partially successful, mission engineers have admitted.

To cope with the condition, engineers have devised an improvised strategy. From now on, Spirit will drive backward on five wheels, rotating the sixth wheel only sparingly to ensure its availability for demanding terrain.

Driving may take us a little bit longer because it is like dragging an anchor, said Joe Melko, a rover engineer at JPL. However, this approach will allow us to continue doing science much longer than we ever thought possible.

Last Thursday, Spirit drove over what scientists had been hoping to find in the hills -- a slab of rock outcrop that may represent some of the oldest rocks observed in the mission so far.

Spirit is now rolling slowly up the Columbia hills.

A few months ago, we weren't sure if we'd make it to the hills, and now here we are preparing to drive up into them, said Matt Golombek, a rover science team member. It's very exciting.

Opportunity has been rolling down Endurance crater to investigate a row of sharp, teeth-like features dubbed Razorback, which may have formed when fluid flowed through cracks, depositing hard minerals. NASA scientists said they hope the new data will help put together the pieces of Meridiani's watery past.

Razorback may tell us more about the history of water at Endurance Crater, said Jack Farmer, a rover science team member from Arizona State University in Tempe.

Phil Berardelli is UPI's Science & Technology Editor. E-mail [email protected]