This could be the Indian summer of Mars exploration.
The success of NASA's Phoenix lander has capped a decade of robotic derring-do and discoveries by uncovering chips of ice on the barren surface of the Red Planet's north pole. The find proves the existence of water, a key ingredient of life.
"It's such a thrill to find ice under our lander," said Peter Smith of the University of Arizona, chief scientist of the Phoenix mission, at a news conference in June.
But economic and political uncertainties are casting doubt on the future of such exploration as budgets are cut, priorities are questioned and the unknowns about the next president shadow the horizon.
Democrat Barack Obama has called for debate on NASA's goals, and his opponent, John McCain, who says he supports manned missions to Mars, has called for a freeze on federal spending.
"In the first year of an Obama or McCain administration, there will be some hard decisions to make regarding NASA," says Eligar Sadeh of the Air Force Academy's Eisenhower Center for Space and Defense Studies in Colorado Springs.
In the popular imagination, Mars has been a goal of U.S. space exploration since the days of controversial rocket expert Wernher von Braun, the leader of the team that developed the V-2 ballistic missile for the Nazis during World War II.
After the war, von Braun worked first for the U.S. Army and then for NASA. In 1952, he outlined a Martian expedition in the magazine Collier's. His proposal, to ship 70 astronauts in 10 spaceships on a one-way trip to Mars, eventually reached 42 million U.S. homes in a 1956 series, The Exploration of Mars, broadcast on Walt Disney Presents.
The appeal of Mars
Such grandiose notions died in the 1970s after the Apollo lunar landings revealed the costs and dangers of manned spaceflight. But Mars still commands great interest from the public and scientists alike.
"Mars is the planet, although it's very different, that is most Earth-like in our solar system," says A. Thomas Young, a retired Lockheed Martin manager and vice chair of the National Research Council's Space Studies Board. "Every time we go there, we are pleasantly surprised by the results.
"Phoenix is just the latest example. And Mars is one of those things that has really captured the imagination of the public."
Since July 4, 1997, when the Mars Pathfinder rover riveted the nation with Martian vistas, the space agency has spent about $5 billion on Mars exploration. The goal has always been to look for signs that water either exists or existed, which would indicate the possibility of life, even if it's just microscopic.
Water on Mars makes a difference for people on Earth for at least three reasons, says Michael Meyer, science chief of NASA's Mars Exploration Program. Exploring Mars may clear up the mystery behind the disappearance of its once-thick atmosphere and surface water, he says, and help us understand our own climate.
Second, Mars may preserve the best record of conditions in the solar system at the time life started on Earth, as well as holding remnants of its own early life.
Third, "Mars could be a future home," Meyer says. Water makes habitation a more likely prospect.
NASA has five Mars probes in action that arrived on the planet in this decade:
•Mars Odyssey (2001), a $300 million orbiter that scans Mars for signs of past water and volcanic activity. The probe reported indications of ice under the Martian surface in 2002.
•Mars Exploration Rovers Spirit and Opportunity (2004). The $830 million doughty rovers, still exploring Mars, discovered water-layered rock in Martian craters.
•Mars Reconnaissance Orbiter (2006). The $720 million orbiter scans Mars for future landing sites, studies weather and makes high-resolution maps.
•Phoenix (2008). The $420 million lander recently dug up ice cubes on Mars and reported water vapor in a soil sample.
"The things we are doing on Mars are going to be remembered in a millennia when the planets are explored," Meyer says. "It is one thing we do as a nation that provides inspiration to people everywhere, who see us exploring our solar system."
A question of money
In 2004, President Bush outlined his "Vision for Space Exploration," a strategy for finishing the International Space Station and retiring the space shuttle by 2010. A new spacecraft would land people on the moon by 2020. "With the experience and knowledge gained on the moon, we will then be ready to take the next steps of space exploration: human missions to Mars and to worlds beyond," Bush said.
Says space policy expert John Logsdon of George Washington University, "The president's strategy was actually a good one — well-thought-out with reasonable targets and milestones."
But the extra money to support the plan and NASA's science goals hasn't come through in an era of budget deficits and a costly war in Iraq, Logsdon says. "Neither the White House nor Congress, with a few notable exceptions, seems to care."
At NASA, the economic fallout has led to cutbacks:
•The president's 2009 budget request cuts Mars spending in half from 2007 to 2010, down to $300 million.
•A proposed 2018 Mars sample-return mission will be deferred, Meyer says. The mission would send soil, rock and other samples back to Earth by rocket.
•Science chief S. Alan Stern resigned in April after his move to trim $4 million from the Mars rovers to help pay for a $200 million overrun in construction of the Mars Science Laboratory was rejected by NASA administrator Mike Griffin. The $2 billion science lab is scheduled to land on Mars in 2010.
"Why are we even contemplating sending people to Mars someday?" asks federal science spending expert Al Teich of the American Association for the Advancement of Science in Washington, D.C. "Robotic mission seems to be generating plenty of excitement."
Says David Goldston, former chief of staff for the House Science Committee and columnist at Nature magazine: "One big misconception people have is that NASA is spending a lot of money on sending people to Mars. It doesn't really spend anything."
In fact, Congress barred NASA from spending any money on Mars astronauts in 2008, and the agency didn't ask for any in next year's budget. Most of the $8 billion NASA spends on manned missions goes to the space shuttle program, the International Space Station and Constellation, the new manned rocket intended for trips to the station in 2015 and the moon in 2020.
Although the Smithsonian Air & Space Museum in Washington opened a Space: A Journey to Our Future exhibit in June (sponsored by NASA, General Motors and Lockheed Martin) that features a Mars base station, NASA doesn't have any astronaut landings planned for Mars.
So what now?
For the future, the space agency contemplates Mars missions in 2013 and 2016 in addition to next year's small-car-size Mars Science Laboratory.
But the next president could shift NASA's focus away from Bush's lunar exploration vision and toward the need to address climate change or forge more global partnerships, says Sadeh.
Mars exploration would fit comfortably in a NASA refocused on climate, says David Grinspoon of the Denver Museum of Natural Sciences, a mission scientist for both Mars and Venus probes. The Red Planet's atmosphere is comparable to Earth's, and atmospheric measurements there have already begun.
Among planetary scientists, there is some feeling that NASA has slighted other planets for Mars, Grinspoon says. Venus is closer than Mars and has its own bizarre atmosphere, for example, and Jupiter's icy moons are a priority for planetary scientists.
"And the impression I get is that NASA headquarters is aware of the concern," he says. "Of course, against the backdrop of huge financial challenges agency-wide, managers there are stuck between a rock and a hard place in making exploration decisions."
Space scientist Lennard Fisk of the University of Michigan, who heads the National Resource Council's Space Studies Board, says, "NASA's programs are inconsistent with the budget the agency possesses."
Last year, the board said NASA hasn't spent enough on other programs, such as the Deep Space Network, which facilitates communications with satellites via high-powered antennas placed around the world.
Fisk sees "a mismatch between what NASA is being asked to do and the resources it has for space science. There's going to be a train wreck at some point." If NASA keeps deferring missions such as the Mars sample-return probe, he contends, the costs to keep the programs alive will eat into the budget without providing the science needed for future exploration. His reservations aside, Fisk states, "Any country that can spend $800 billion on a war in Iraq can afford a space program." NASA's entire $17 billion budget, he notes, equals the exploration tax breaks given to oil companies every year.
"The real problem is that NASA needs to be tied to a real, overriding national priority," he says, such as protecting the planet from asteroids or controlling global warming. "Otherwise, NASA will just limp along."