Planetary scientists have discovered pieces of opal in a meteorite found in Antarctica, a result that demonstrates that meteorites delivered water ice to asteroids early in the history of the solar system. Opal, familiar on Earth as a precious stone used in jewellery, is made up of silica (the major component of sand) with up to 30 percent water in its structure.
Mars’ gullies may be formed by dry ice processes rather than flowing liquid water, as previously thought. This is the conclusion of a study conducted by two French scientists published in Nature Geoscience. They show that, during Martian late winter and spring, underneath the seasonal CO2 ice layer heated by the Sun, intense gas fluxes can induce gas-lubricated debris flows which look like water-sculpted gullies on Earth.
NASA’s Cassini mission scientists were watching closely when the Sun set on Saturn’s rings in August 2009. It was the equinox — one of two times in the Saturnian year when the Sun illuminates the planet’s enormous ring system edge-on — providing an extraordinary opportunity for the spacecraft to observe short-lived changes that reveal details about the nature of the rings.
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