The ability of NASA's Mars Reconnaissance Orbiter to continue charting the locations of these hidden glaciers and ice-filled valleys -- first confirmed by radar two years ago -- adds clues about how these deposits may have been left as remnants when regional ice sheets retreated.
The subsurface ice deposits extend for hundreds of kilometers, or miles, in the rugged region called Deuteronilus Mensae, about halfway from the equator to the Martian north pole. Jeffrey Plaut of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues prepared a map of the region's confirmed ice for presentation at this week's 41st Lunar and Planetary Science Conference near Houston.
The Shallow Radar instrument on the orbiter has obtained more than 250 observations of the study area, which is about the size of California.
"We have mapped the whole area with a high density of coverage," Plaut said. "These are not isolated features. In this area, the radar is detecting thick subsurface ice in many locations." The common locations are around the bases of mesas and scarps, and confined within valleys or craters.
Plaut said, "The hypothesis is the whole area was covered with an ice sheet during a different climate period, and when the climate dried out, these deposits remained only where they had been covered by a layer of debris protecting the ice from the atmosphere."
thinkahol * on 04 Nov 10A new study in The Lancet rates the harmfulness of 20 psychoactive drugs according to 16 criteria and finds that alcohol comes out on top. Although that conclusion is generating headlines, it is not at all surprising, since alcohol is, by several important measures (including acute toxicity, impairment of driving ability, and the long-term health effects of heavy use), the most dangerous widely used intoxicant, and its abuse is also associated with violence, family breakdown, and social estrangement. A group of British drug experts gathered by the Independent Scientific Committee on Drugs (ISCD) rated alcohol higher than most or all of the other drugs for health damage, mortality, impairment of mental functioning, accidental injury, economic cost, loss of relationships, and negative impact on community. Over all, alcohol rated 72 points on a 100-point scale, compared to 55 for heroin, 54 for crack cocaine, and 33 for methamphetamine. Cannabis got a middling score of 20, while MDMA (Ecstasy), LSD, and psilocybin mushrooms were at the low end, with ratings of 9, 7, and 6, respectively.
