Tag archives: ocean
By Hamish Johnston
This week’s Red Folder is inspired by a vision I had last night while I was putting out the garbage bins. I happened to look up at the sky just as the International Space Station (ISS) was travelling over Bristol. It was a very bright and impressive sight as it zipped overhead before disappearing at the eastern horizon. If you happen to be on an arc through northern Europe between Penzance and Poznań, you should also have a great view of the ISS this evening; you can find out when and where to look at the ISS Astroviewer website.
The ISS is one thing that you would definitely not see if you could look at the sky as it was 10 billion years ago – but have you ever wondered what that view would be? Zolt Levay at the Hubble Heritage Information Center has, and the above image is his vision of what the sky would look like from a hypothetical planet within a Milky Way-like galaxy 10 billion years ago. The work was inspired by a new collection of nearly 2000 images of galaxies as they appeared at that time in the history of the universe. Taken by a number of different telescopes including Hubble, “the new census provides the most complete picture yet of how galaxies like the Milky Way grew over the past 10 billion years into today’s majestic spiral galaxies”, according to NASA.
Cassini’s enhanced and false-coloured image of Enceladus backlit by the Sun shows the fountain-like plumes of the fine spray of material that spews from the south polar region (Courtesy: NASA/JPL/Space Science Institute)
By Tushna Commissariat
Enceladus, Saturn’s sixth largest moon is back in the news as the Cassini-Huygens mission has managed to directly sample the water plumes jetting into space from its southern polar region. These plumes of ice and salt originate from the moon’s famed “tiger stripes” region – four parallel giant fissures on the southern face of the moon.
The findings from these fly-throughs are the strongest evidence yet for the existence of large-scale saltwater reservoirs beneath the moon’s icy crust. “Enceladus is a tiny icy moon located in a region of the outer solar system where no liquid water was expected to exist, because of its large distance from the Sun,” says Nicolas Altobelli, ESA’s project scientist for the Cassini-Huygens mission. “This finding is therefore a crucial new piece of evidence showing that environmental conditions favourable to the emergence of life may be sustainable on icy bodies orbiting gas-giant planets.”
Indeed, the moon has been described previously by other Cassini researchers as one of the “most habitable spots beyond Earth in the solar system for life as we know it”.
Enceladus’ water plumes are though to contribute towards replenishing Saturn’s outermost and faint E-ring, which traces the orbit of Enceladus around Saturn. The Cassini spacecraft discovered the plumes in 2005 and more recently has been able to fly directly through them.
During three of Cassini’s passes in 2008 and 2009, its Cosmic Dust Analyser measured the composition of freshly ejected plume grains. The icy particles hit the detector target at speeds of 6.5–17.5 km/s, and vaporized instantly. Electrical fields inside the instrument then separated the various constituents of the resulting impact cloud for analysis.
Researchers looking at the data from the detector have found that grains ejected in the plumes and into the atmosphere of the moon and out towards the E-ring are relatively small and mostly salt-poor, closely matching the composition of the E-ring. However, closer to the moon itself relatively large, salt-rich ice grains were found.
This mosaic of 21 Cassini images is a false colour full-disc view of the anti-Saturn hemisphere on Enceladus (Courtesy: NASA/JPL/Space Science Institute)
Scientists explain this by saying that more than 99% of the total mass of ejected solids is in salt-rich grains, but most of these are heavy and fall back to the moon, so never make it into the E-ring. The salt-rich particles have an “ocean-like” composition which indicates that most, if not all, of the expelled ice comes from liquid saltwater body somewhere under the surface, rather than from the icy face of the moon.
The scenario envisioned by the team goes something like this – deep underneath Enceladus’ surface, perhaps 80 km down, there is a reservoir of water between the rocky core and the icy mantle, kept liquid by tidal forces generated by Saturn and its neighbouring moons, as well as by the heat generated by radioactive decay. When the outermost layer cracks open, the reservoir is exposed to space. The drop in pressure causes the liquid to evaporate, with some of it flash-freezing into salty ice grains: together these create the plumes.
When salty water freezes slowly, the salt is squeezed out, leaving pure water ice behind. So, if the plumes were coming from the surface ice, there should be very little salt in them. “There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across the tiger stripes other than from saltwater under Enceladus’ icy surface,” says Frank Postberg, Universität Heidelberg, Germany, who is the lead author of a Nature paper announcing these results.
Artist’s impression of a map of the Quantum Universe (Graphic courtesy of “ILC — form one visual communication”)
By Tushna Commissariat
Here’s a bit of Friday physics fun… I came across this rather interesting image that shows an artist’s impression of a map entitled “The Quantum Universe”. It includes six landmasses all floating in the Big Bang Ocean; including Dark Matter Landmass, Sypersymmetry Reef, Higgs Island and the Land of Ultimate Unification as well as others.
So go ahead and tell us which island you would like to settle down on. Be sure to look carefully at gems like Newton’s Lawn and Mount Einstein before you make your mind up!
To see a larger hi-res image follow this link.