We've already seen water ice on Mars. NASA's Phoenix lander will reach out and touch it.
- By Charles Petit
- Air & Space magazine, August 2007
(Page 4 of 5)
In August 2003, NASA selected Phoenix as its inaugural Scout mission. Smith’s proposal beat two dozen others, including one that would have returned samples of the Martian atmosphere to Earth. Mike Meyer, the senior scientist for NASA’s Mars exploration program, is all in favor of resurrecting the goals of an approved but never-realized mission: “Mars Polar Lander was built for a very good reason, and Phoenix recaptures many of its advantages,” he says. “It should give us a very good idea what that ice is made of, and also what the seasonality of Mars is and how that fits into long-term orbital cycles and climate change.” That information, combined with remote sensing data from other spacecraft, could help scientists plan future Mars missions by suggesting regions where water is likely to have flowed in the past.
It hasn’t been all smooth sailing since the NASA selection. The space agency has become more cost-conscious than ever, and if a Scout spacecraft can’t be built properly within the approved budget, says Smith, it either gets scrapped or is scaled back to match the available funds. Despite the team’s best efforts, it ran its budget dry. Into the discard heap went a radio transmitter, called the X-band antenna, which would have enabled Phoenix to transmit data directly to Earth. Now the only means of communication will be through the two spacecraft already circling the planet, the Mars Odyssey and the Mars Reconnaissance Orbiter, which will act as relays. The 1999 failures taught NASA one important lesson, however. Phoenix will continue transmitting data and reports on its condition all the way from atmospheric entry to touchdown. If something goes wrong during descent, mission managers will at least know what happened. Losing a spacecraft is bad enough, says Smith; never finding out why “is just horrible.”
Late last year the project team let NASA know it was having money trouble. The biggest headache had been the landing radar, or altimeter. The original unit was inherited from the stored 2001 lander. Adapted from an altimeter used on F-16 fighters, “it was old when they put it in,” Smith says. “The Air Force doesn’t use this one anymore. We couldn’t even get parts, and the guys who knew it best had retired.” Tests revealed its performance was erratic, making data dropouts at critical times possible. The engineers spent months, with Lockheed doing much of the work, making a reliable altimeter.
The project’s budget had included a reserve fund for just these kinds of unexpected problems. Even so, the extra altimeter work, combined with fixes for other glitches and the late scramble to find a safe landing zone, put Phoenix tens of millions of dollars over the $386 million cap NASA had set for the mission. The team had been warned that a cost overrun would set off a formal NASA termination review. One was held in late January. After Phoenix passed, Smith said it had been unlikely all along that NASA would actually cancel a mission so close to launch. But he did tell a Rocky Mountain News reporter that watching the bills run up had kept him in agony for months.
Even with the overrun, if Phoenix continues the Mars program’s current string of successes, NASA will likely consider its money well spent. Since the 1999 loss of the Mars Polar Lander, the news has been all good: Mars Odyssey (launched in 2001 to further the study of Martian geology and weather), the twin rovers, and the Mars Reconnaissance Orbiter (launched in 2005) all arrived safe and sound, and all four are still working. The orbiters are busily mapping the composition of the atmosphere and the surface, as well as using ground-penetrating radar to explore the subsurface. The Mars Express, a European orbiter with a suite of powerful cameras and other sensors, has performed flawlessly. The Spirit and Opportunity rovers have delighted their operators by running well into their third year and traveling a combined total of more than 11 miles.
If Phoenix does find traces of organic materials and conditions suitable for life, or if it just helps scientists understand how water cycles between the ground and the atmosphere, it will shape the scientific questions to be answered by subsequent Mars missions. Favorable launch windows (meaning those that require the least amount of rocket fuel to reach the planet) come around every 26 months, and NASA tries to hit every window. Next up after Phoenix is a long-range rover called the Mars Science Laboratory, which in 2009 will carry an even more advanced organic chemistry lab to extend the search for life. Another Scout mission, still to be selected, is slated for the following opportunity, in 2011. Beyond that, things become uncertain. NASA’s Mars program has gotten leaner in recent years as the agency has shifted money from space science into preparations to send astronauts back to the moon. A Mars sample-return mission, once the program’s highest priority, has been pushed off into an indefinite future.
Most scientists believe such a mission will eventually be necessary, not only to answer questions about the possibility of Martian life but to help engineers prepare for an astronaut landing. There is some evidence that the soil may be toxic or corrosive, and NASA would want to carefully analyze it before designing spacesuits and other equipment for human explorers.
Until then, look for more Scouts like Phoenix to fill the gaps between the big, expensive missions and to pioneer a new approach to the continuing exploration of the second most visited planet in the solar system.