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Origin of glaciers on Mars EUROPEAN SPACE AGENCY NEWS RELEASE Posted: January 20, 2006 The spectacular features visible today on the surface of the Red Planet indicate the past existence of Martian glaciers, but where did the ice come from?
Moreover, the results of the simulations show for the first time that the predicted locations for these glaciers match extensively with many of the glacier remnants observed today at these latitudes on Mars. For several years, the presence, age and shape of these glacier remnants have raised numerous questions in the scientific community about their formation, and about the conditions on the planet when this happened. To start narrowing down the rising number of hypotheses, a team led by Francois Forget, University of Paris 6 (France) and interdisciplinary scientist for ESA's Mars Express mission, decided to "turn back the clock" in their Martian global climate computer model, a tool usually applied to simulate the detail of present-day Mars meteorology. As a starting point, Forget and colleagues had to make some assumptions - that the north polar cap was still the ice reservoir of the planet, and that the rotation axis was tilted by 45 degrees with respect to the planet's orbital plane. "This makes the axis much more oblique than it is today (about 25 degrees), but such an obliquity has probably been very common throughout Mars's history. Actually, it last occurred only five and a half million years ago," says Forget. As expected with such a tilt, the greater solar illumination in the north polar summer increased the sublimation of the polar ice and led to a water cycle much more intense than today. The simulations showed water ice being accumulated at a rate of 30 to 70 millimetres per year in a few localised areas on the flanks of the Elysium Mons, Olympus Mons and the three Tharsis Montes volcanoes. After a few thousand years, the accumulated ice would form glaciers up to several hundreds of metres thick. When the team compared the location and shape of the "simulated" glaciers with the actual glacier-related deposits of Tharsis - one of the three main regions on the planet where signs of glaciers are seen - they found an excellent agreement. In particular, the maximum deposition is predicted on the western flanks of the Arsia and Pavonis Montes of the Tharsis region, where the largest deposits in this area are actually observed. In their simulations, the team could even "read" why and how ice was accumulated on the flanks of these mountains in the Tharsis region millions of years ago. Back then, constant year-long winds similar to monsoons on Earth would favour the upslope movement of water-rich air around Arsia and Pavonis Montes. While being cooled down by tens of degrees, water would condense and form ice particles (larger than those we observe today in the Tharsis region's clouds) that settled on the surface. Other mountains like Olympus Mons show smaller-scale deposits because, according to the simulations, they were exposed to the monsoon-type strong winds and water-rich air only during the northern summer. "The north polar cap may not have always been the only source of water during the planet's high obliquity periods," adds Forget. "So we ran simulations assuming that ice was available in the south polar cap. We could still see ice accumulation in the Tharsis region, but this time also on the east of the Hellas Basin, a six-kilometre deep crater." This would explain the origins of another major area where ice-related landforms are observed today, the eastern Hellas Basin, indeed. "The Hellas basin is in fact so deep as to induce the generation of a northward wind flow on its eastern side that would carry most of the water vapour sublimating from the south polar cap during summer. When the water-rich air meet colder air mass over eastern hellas, water condense, precipitate, and form glaciers," said Forget. However, the team could not predict ice deposition in the Deuterolinus-Protonilus Mensae region, where glaciers could have been formed by other mechanisms. The scientists are considering several other hypotheses on the formation of recent glaciers. For instance, observations of Olympus Mons by the High Resolution Stereo Camera on board Mars Express suggest that movement of water from the subsurface to the surface due to hydrothermal activity may have led to the development of glaciers on the cold surface. The results appear in today's issue of the scientific journal Science, in an article titled "Formation of glaciers on Mars by atmospheric precipitation at high obliquity," by: F. Forget (Laboratoire de Meteorologie Dynamique, Institut Pierre Simon Laplace (IPSL), France), R.M. Haberle (NASA Ames Research Center, USA), F. Montmessin (Service d'Aeronomie, IPSL, France), B. Levrard (Inst. de Mecanique Celeste, Paris, France), J.W. Head (Brown Univ., Rhode Island, USA). The Martian global climate computer model is a tool designed by the Laboratoire de Meteorologie Dynamique, (France) with the support of CNRS, ESA and CNES. It is used to simulate the present-day climate on Mars and so support the analysis of many of the current observations at Mars, including those of ESA's Mars Express. The version used here provides the distribution of atmospheric vapour and clouds; it describes the exchange between surface ice and atmospheric water, transport and turbulent mixing of water in the atmosphere, and the microphysics of cloud formation. |
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The New Horizons spacecraft begins a voyage across the solar system to explore Pluto and beyond with its successful launch January 19 aboard a Lockheed Martin Atlas 5 rocket from Cape Canaveral, Florida.
NASA's Stardust spacecraft returns samples of cometary dust to Earth with its safe landing in Utah on January 15.
NASA Administrator Mike Griffin and his deputy Shana Dale hold a news conference at Kennedy Space Center in the final hours of the countdown to the New Horizons launch. Questions from reporters ranged from the Pluto-bound mission, the agency's budget and the space shuttle program.
Space shuttle Columbia's mission in January 1990 sought to retrieve the Long Duration Exposure Facility -- a bus-size platform loaded with 57 experiments -- that had been put into orbit six years earlier. LDEF was supposed to be picked up within a year of its launch. But plans changed and then the Challenger accident occurred. Columbia's STS-32 crew got into space, deployed a Navy communications satellite, then fulfilled their LDEF recovery mission, carried out a host of medical tests and returned to Earth with a nighttime touchdown in the California desert. The crew presents this post-flight film of mission highlights.
This film looks at the highlights in NASA's history from its creation in the 1950s, through the glory days of the Mercury, Gemini and Apollo programs, birth of the space shuttle and the loss of Challenger, launch of Hubble and much more.
If at first you don't succeed, keep on trying. That is what the astronauts of space shuttle Endeavour's maiden voyage did in their difficult job of rescuing a wayward communications satellite. Spacewalkers were unable to retrieve the Intelsat 603 spacecraft, which had been stranded in a useless orbit, during multiple attempts using a special capture bar. So the crew changed course and staged the first-ever three-man spacewalk to grab the satellite by hand. The STS-49 astronauts describe the mission and narrate highlights in this post-flight presentation.
The mission for the crew of space shuttle Challenger's April 1984 flight was two-fold -- deploy the experiment-laden Long Duration Exposure Facility (LDEF) and then track down the crippled Solar Max spacecraft, capture it and perform repairs during spacewalks. Initial attempts by the astronauts to grab the craft while wearing the Manned Maneuvering Unit spacewalk backpacks failed, but the crew ultimately retrieved Solar Max and installed fresh equipment while it was anchored in the payload bay. The crew narrates this post-flight presentation of home movies and highlights from mission STS-41C.
The space shuttle program was grounded for 32 months in the painful wake of the 1986 Challenger accident. Americans finally returned to space in September 1988 when shuttle Discovery safely launched for its mission to deploy a NASA communications satellite. Enjoy this post-flight presentation narrated by the astronauts as they show movies and tell the story of the STS-26 mission.
Imagine a space shuttle mission in which the astronaut crew launched two commercial and one military communications spacecraft, then conducted a pair of incredible spacewalks to recover, fix and redeploy a satellite that malfunctioned just four months earlier. The rescue mission was a success, starting with an astronaut making a catch of the spinning satellite with just his gloved-hand. Enjoy this post-flight presentation narrated by the astronauts as they tell the story of shuttle Discovery's August 1985 mission known as STS-51I.
