A NASA study calls for a series of unmanned and manned missions to Mars that, if implemented, would mean humans would be walking on Mars as early as 2010.
     The NASA study, reported by Space News, calls for three launches to Mars during each Earth-Mars launch opportunity starting in 2007. Such launch windows open every 26 months.
     After three cargo missions deliver hardware to the surface of and in orbit around Mars in 2007, a manned mission and two cargo missions would depart in late 2009 for a 180-day trip to Mars. Similar launches would take place in 2012 and 2014.
     Each six-person crew would stay on Mars for 18 to 20 months. During the stay they would manufacture propellants for a "Mars ascent" vehicle which the crew would use to leave the surface and rendezvous with an Earth-return vehicle in Martian orbit. The first Mars-ascent and Earth-return vehicles would be launched in 2007, and again in each future launch window.
     The goal of the program is to establish a permanent presence on Mars by the year 2016. The first three crews would work to build a "basic infrastructure" at the base to be used for permanent habitation.
     The study estimated the cost of the program through 2016 to be about $40 billion. This is less than one-tenth the cost of the original "90-Day Study" NASA and contractors released for the Space Exploration Initiative at the beginning of the decade.
     The price tag may still be too large for a space agency fighting budget cuts every year, though. "The magnitude [of the cost] is probably still too high in today's fiscal environment," the report states, according to Space News. "More work to further reduce these costs is needed."
     The report was drafted at the Johnson Space Center's Exploration Projects Office. NASA headquarters has been reviewing a draft of the report but has not yet officially approved it.

Astronomers studying the poles of the Moon with the world's largest radio telescope have failed to find evidence of water ice, raising doubts about the discovery of water ice by the Clementine spacecraft announced last year.
     "We don't see anything that suggests ice," said Cornell University astronomy professor Donald Campbell. "We don't think there is any obvious evidence from the Arecibo radar images for the presence of water ice at the poles of the Moon."
     Campbell, with then-graduate student Nicholas Stacy and MIT scientist Peter Ford, used the giant 300-meter (1,000-foot) radio telescope at Arecibo, Puerto Rico, to look at poles of the Moon in 1992 using the same radar wavelength, 13 cm, as the Clementine spacecraft used two years later.
     The team reported that they found small patches, little more than a square kilometer (one-half square mile) in size, where the reflection of radar signals could be interpreted as ice. However, they found such patches on other areas of the moon which are sunlit and thus where ice could not exist.
     Campbell and his team believe the signals are more likely caused by rough surfaces associated with impact craters, and not water ice. "Our contention is that the surface roughness is a much better candidate for the signatures we're seeing," he said.
     Scientists using data collected by the Clementine spacecraft in 1994 announced last December that they had found evidence for deposits of water ice in permanently-shadowed regions of the Moon's south pole. In those areas temperatures stay cold enough to keep the ice from sublimating. Some have proposed using those deposits as a source of water for future lunar missions.
     Campbell said, though, that the case was not closed on the possibility of lunar water ice. "However, neither Arecibo nor Clementine observed all the areas that are in permanent shadow and there is still the possibility that there are ice deposits in the bottoms of deep craters."
     Lunar Prospector, a NASA spacecraft scheduled for launch this September, should be able to take a better look and confirm or deny the existence of lunar ice.

Astronaut Jerry Linenger, who returned to Earth last month after four months on the Russian space station Mir, discussed his time on Mir and his readaptation on Earth at a press conference June 13 and in a previous interview.
     At the press conference, Linenger said the numerous problems with the station during his time there -- which included a flash fire, coolant leaks, and faulty oxygen generators -- were bothersome but not a complete distraction.
     "The time on the station was probably more challenging than I expected," he said.
     However, in a previous interview with Reuters, Linenger described the problems as more severe. "You feel like all you're doing is just trying to stay alive," he said. "You say to yourself 'what are we accomplishing here other than just existing?'"
     Linenger told Reuters he often worked into the night to complete work on experiments that he did not have time during the day to complete, due to repair work on the station.
     Of all the problems with Mir, Linenger said he thought leaks in the corroded pipes in the cooling system were the most serious. "It's a fundamental part of the Mir; it's like the foundation of a house," he said. "The corrosion in the cooling loops might be the show stopper."
     Linenger said he is enjoying doing "basic things we all take for granted" back on Earth, such as some simple gardening work he did in the backyard of his home the first morning after he returned from space. He is also exercising and following a diet to build up lost bone and muscle mass.
     Linenger, who will become a father for the second time later this month, said he is making plans for a career outside NASA and may soon retire from the astronaut corps. "Right now the number-one choice is just to retire," he told Reuters. "I had one heck of an adventure and I survived."

NASA and the U.S. Department of Defense are making plans to use current and future spacecraft to look for additional evidence that small comets are striking the Earth at a high rate.
     NASA is considering a dedicated mission to search for and study these small comets as they strike the Earth, George Withbroe, science director for the Sun-Earth Connection program at NASA, told Space News. Withbroe said he expected one or more proposals for such missions under the Small Explorer program by a June 16 deadline.
     Withbroe also said that NASA will investigate ways of using Mars-bound spacecraft to look for evidence of these bodies striking the Red Planet. "We will be looking at what other types of existing platforms can be used to study this," he told Space News.
     The Defense Department is also reportedly talking with NASA about using military spacecraft to search for these comets as they break apart and burn up in the uppermost reaches of the Earth's atmosphere.
     These new studies were prompted by data released by University of Iowa researcher Louis Frank at a meeting of the American Geophysical Union May 28. At the meeting, Frank showed data taken from NASA's Polar spacecraft which showed small bodies burning up high above the Earth. Frank says the objects are small comets, about the size of a house and weighing about 20 tons.
     Frank originally proposed that small comets were striking the Earth at high rates in the mid-1980s, using black "holes" visible in ultraviolet images of the Earth's atmosphere taken with another satellite. At the time the holes were dismissed by many as instrumental errors.
     Many members of the scientific community are still unconvinced by Frank's evidence, pointing to a lack of other observed evidence of small comets striking the Earth's atmosphere or other worlds.