Random Linkage 19/12/09
Glint of Sunlight Confirms Liquid in Northern Lake District of Titan
'NASA’s Cassini Spacecraft has captured the first flash of sunlight reflected off a lake on Saturn’s moon Titan, confirming the presence of liquid on the part of the moon dotted with many large, lake-shaped basins. '
Enceladus plume is half ice
'As much as 50% of the plume shooting out of geysers on Saturn's moon Enceladus could be ice, a researcher revealed yesterday at a meeting of the American Geophysical Union in San Francisco, California.'
(No misty caves, then, but this doesn't rule out liquid water - unless the clatherate champions are right...)
Searching for Activity on Saturn’s Mid-size Moons
'Like midnight taggers, Saturn’s moons Dione, Tethys, Mimas and Rhea may be spraying their unique signatures all over Saturn’s environment when no one’s looking. Or maybe not; they’ve never been caught in the act, unlike their sibling moon Enceladus, which has been repeatedly observed shooting a dramatic plume of ice vapor high above its surface.
'Other than Enceladus, there are just a handful of active moons in the solar system. Icy geysers shoot from the surface of Neptune’s Triton and Jupiter’s Io is wildly alive with molten sulfur volcanoes. There is some evidence that Jupiter’s Europa may be active, and a future mission is being planned to take a closer look. These rare worlds provide a window on the processes that shape different planetary environments.'
(Well, you can count out Rhea, actually - that’s officially as dead as a doornail. But if there is any evidence of activity on the other large inner moons, it changes the entire game (and makes the need for a new mission to Saturn even more urgent)).
Hubble Finds Smallest Kuiper Belt Object Ever Seen
'Like finding a needle in a haystack, the Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt. While Hubble didn't image this KBO directly, its detection is still quite impressive. The object is only 975 meters (3,200 feet)across and a whopping 6.7 billion kilometers (4.2 billion miles) away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 48 km (30 miles) across, or 50 times larger. This provides the first observational evidence for a population of comet-sized bodies in the Kuiper Belt.'
Astronomers Find Super-Earth Orbiting Red Dwarf Star; May Have Atmosphere
'Astronomers announced that they have discovered a "super-Earth" orbiting a red dwarf star 40 light-years from Earth. They found the distant planet with a small fleet of ground-based telescopes no larger than those many amateur astronomers have in their backyards. Although the super-Earth is too hot to sustain life, the discovery shows that current, ground-based technologies are capable of finding almost-Earth-sized planets in warm, life-friendly orbits.'
(Atmosphere is most likely a raging hell of superheated steam, but it’s still an impressive result. How hard would it be for backyard astronomers to set up their own networks and search for exoEarths?)
Mammals May Be Nearly Half Way Toward Mass Extinction
'If the planet is headed for another mass extinction like the previous five, each of which wiped out more than 75 percent of all species on the planet, then North American mammals are one-fifth to one-half the way there, according to a University of California, Berkeley, and Pennsylvania State University analysis.'
(Next: either the age of the birds, or the return of the reptiles. And this before climate change really kicks in.)
Probabilistic assessment of sea level during the last interglacial stage
'With polar temperatures ~3–5 ̊C warmer than today, the last interglacial stage (~125 kyr ago) serves as a partial analogue for 1–2 ̊C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (?-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr-1 but is unlikely to have exceeded 9.2 m kyr-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.'
(In other words, don’t buy property less than 6 metres above present sea level. But do buy a boat. Oh yeah, currently some 145 million people live within one metre of current sea levels.)
'NASA’s Cassini Spacecraft has captured the first flash of sunlight reflected off a lake on Saturn’s moon Titan, confirming the presence of liquid on the part of the moon dotted with many large, lake-shaped basins. '
Enceladus plume is half ice
'As much as 50% of the plume shooting out of geysers on Saturn's moon Enceladus could be ice, a researcher revealed yesterday at a meeting of the American Geophysical Union in San Francisco, California.'
(No misty caves, then, but this doesn't rule out liquid water - unless the clatherate champions are right...)
Searching for Activity on Saturn’s Mid-size Moons
'Like midnight taggers, Saturn’s moons Dione, Tethys, Mimas and Rhea may be spraying their unique signatures all over Saturn’s environment when no one’s looking. Or maybe not; they’ve never been caught in the act, unlike their sibling moon Enceladus, which has been repeatedly observed shooting a dramatic plume of ice vapor high above its surface.
'Other than Enceladus, there are just a handful of active moons in the solar system. Icy geysers shoot from the surface of Neptune’s Triton and Jupiter’s Io is wildly alive with molten sulfur volcanoes. There is some evidence that Jupiter’s Europa may be active, and a future mission is being planned to take a closer look. These rare worlds provide a window on the processes that shape different planetary environments.'
(Well, you can count out Rhea, actually - that’s officially as dead as a doornail. But if there is any evidence of activity on the other large inner moons, it changes the entire game (and makes the need for a new mission to Saturn even more urgent)).
Hubble Finds Smallest Kuiper Belt Object Ever Seen
'Like finding a needle in a haystack, the Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt. While Hubble didn't image this KBO directly, its detection is still quite impressive. The object is only 975 meters (3,200 feet)across and a whopping 6.7 billion kilometers (4.2 billion miles) away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 48 km (30 miles) across, or 50 times larger. This provides the first observational evidence for a population of comet-sized bodies in the Kuiper Belt.'
Astronomers Find Super-Earth Orbiting Red Dwarf Star; May Have Atmosphere
'Astronomers announced that they have discovered a "super-Earth" orbiting a red dwarf star 40 light-years from Earth. They found the distant planet with a small fleet of ground-based telescopes no larger than those many amateur astronomers have in their backyards. Although the super-Earth is too hot to sustain life, the discovery shows that current, ground-based technologies are capable of finding almost-Earth-sized planets in warm, life-friendly orbits.'
(Atmosphere is most likely a raging hell of superheated steam, but it’s still an impressive result. How hard would it be for backyard astronomers to set up their own networks and search for exoEarths?)
Mammals May Be Nearly Half Way Toward Mass Extinction
'If the planet is headed for another mass extinction like the previous five, each of which wiped out more than 75 percent of all species on the planet, then North American mammals are one-fifth to one-half the way there, according to a University of California, Berkeley, and Pennsylvania State University analysis.'
(Next: either the age of the birds, or the return of the reptiles. And this before climate change really kicks in.)
Probabilistic assessment of sea level during the last interglacial stage
'With polar temperatures ~3–5 ̊C warmer than today, the last interglacial stage (~125 kyr ago) serves as a partial analogue for 1–2 ̊C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (?-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr-1 but is unlikely to have exceeded 9.2 m kyr-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.'
(In other words, don’t buy property less than 6 metres above present sea level. But do buy a boat. Oh yeah, currently some 145 million people live within one metre of current sea levels.)
posted by Paul McAuley at 3:34 pm
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