We’re getting a closer look at Saturn’s moon Hyperion, the result of data analysis following Cassini’s flyby in September of 2005. Using near-infrared and ultraviolet spectroscopy, researchers have been able to analyze the moon’s surface composition, with results suggestive of water and carbon dioxide ices as well as an analysis of dark material indicating hydrocarbons. That’s a mix of materials not unlike what we’ve found in comets and probably similar to what we’ll detect in Kuiper Belt objects.
Here’s Dale Cruikshank (NASA Ames), lead author on the paper:
“Of special interest is the presence on Hyperion of hydrocarbons — combinations of carbon and hydrogen atoms that are found in comets, meteorites, and the dust in our galaxy. These molecules, when embedded in ice and exposed to ultraviolet light, form new molecules of biological significance. This doesn’t mean that we have found life, but it is a further indication that the basic chemistry needed for life is widespread in the universe.”
We already knew about frozen water on Hyperion, based on earlier ground-based observations, but Cassini also found solid carbon dioxide mixed with ordinary ice that is chemically attached to other molecules. “We think that ordinary carbon dioxide will evaporate from Saturn’s moons over long periods of time,” adds Cruikshank, “but it appears to be much more stable when it is attached to other molecules.”
Image: This is a color map of the composition of a portion of Saturn’s moon Hyperion’s surface about 75 kilometers (45 miles) on a side. In this map, blue shows the maximum exposure of frozen water, red denotes carbon dioxide ice (“dry ice”), magenta indicates regions of water plus carbon dioxide, yellow is a mix of carbon dioxide and an unidentified material. This map was made with data from the Visual and Infrared Mapping Spectrometer aboard the Cassini spacecraft during its flyby of Hyperion in September 2005. Credit: NASA/JPL/University of Arizona/Ames.
More on Hyperion’s hydrocarbons in this news release. Meanwhile, the same issue of Nature contains results from Cassini imaging and radio data collecting during the same flyby. The moon’s sponge-like appearance is attributed to extremely low density. Hyperion turns out to be about half as dense as water. Using the tiny deflection in Cassini’s orbit caused by the flyby, Italian scientists were able to estimate the moon’s mass. This combined with volume data collected by imaging provided density figures.
The porous moon tends to compress under the impact of incoming debris, but what material is ejected from such craters probably doesn’t fall back to the surface due to Hyperion’s low gravity. That gives craters there a crisp, well-defined look that sets them apart from those on denser worlds.
Image: The odd, sponge-like surface of Hyperion. Note the dark centers in some craters. Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA.
The papers are Cruikshank et al., “Surface composition of Hyperion,” Nature 448 (5 July 2007), pp. 54-56 (abstract) and Thomas et al., “Hyperion’s sponge-like appearance,” Nature 448 (5 July 2007), pp. 50-56 (abstract).
The trouble with the ‘basic chemistry for life’ mantra mostly expoused by physicists and not biologists is that hydrocarbons and even amino acids are far less complex than protiens which are far far less organized than a basic cell. This is the astronomer’s somewhat naieve view of biology and life forms. Yes, 50 years ago it was an unexpected surprise that hydrocarbons could exist in interstellar and solar system space, but that’s no longer the case. SOME biologists regard the probaility of the primal arising of ‘life’ as so improbable from a chemistry standpoint that there may be no other life in the universe that that which is present here and has migrated elsewhere via panspermia. Point is, we’re clueless from a factual standpoint. It’s a matter of belief, not science.
Hi philw
The odds are improbable for random assembly, but there’s growing evidence that auto-catalytic systems of small molecules were the very first stage of “life”, and that everything that followed was just one pathway that life might have taken.
As for faith, biochemists trust that biology comes from chemistry, and so far they haven’t been disappointed. There’s no “vital spark”, but there is an information aspect to life that needs explanation. But consider this: a protein a few hundred amino acids long would take trillions of times the age of the Universe to fold up if it had to randomly search through all its possible conformations. Instead it folds in mere seconds. Biomolecules are “smarter” than we give them credit.
http://www.theage.com.au/news/World/Scientists-debunk-comet-ice-life-theory/2007/08/07/1186252680988.html
Scientists debunk comet ice life theory
August 7, 2007 – 12:49PM
For the first time, there is solid data to refute a popular theory that life came to Earth aboard a comet, Rutgers researchers say.
Deteriorated DNA from microbes, frozen for millions of years in the Antarctic ice, shows that organisms could not have survived the bombardment of cosmic radiation during deep space travel from outside the solar system, said Paul Falkowski, a Rutgers biologist and oceanographer.
“It’s almost an impossibility for comets to seed other planets with life after they’ve been in space for millions of years,” Falkowski said.
That’s because genetic material is severely damaged or destroyed by exposure to so-called “cosmic radiation flux”, he said.
Falkowski is co-director of the two-year study of frozen glacial microbes, conducted in conjunction with Boston University, and published in the Proceedings of the National Academy of Sciences.
The researchers were mainly interested in whether genetic material from the microbes, which they identified as different types of bacteria, could have mixed with that of other organisms in the Earth’s ancient oceans, and influenced evolution, Falkowski said.
The Rutgers study refutes at least part of the “panspermia hypothesis” – a theory from the Greeks, and popular among many scientists since the 19th century – that micro-organisms and biochemicals were carried to the planet by comets, meteors and asteroids.
Other scientists in New Jersey said that they were intrigued by the Rutgers study, but suggested there might be ways some organic material could survive long-term rides on a comet.
“The only question I’d have is whether the radiation can penetrate into the interior of a comet,” said Dale Gary, an astrophysicist at the New Jersey Institute of Technology in Newark.
Comets are called “dirty snowballs”, which implies there is a certain amount of rocky material at their centre which could provide a shield for travelling DNA, Gary said.
“Certainly anything on the surface of comets would suffer radiation damage,” he said. Gary, chairman of physics at NJIT, had not seen the study.
“Perhaps they (Rutgers) have done some calculation of the penetration of these cosmic rays through ice, and concluded that, for a certain radius, it can destroy DNA deep inside.
“However, we don’t know everything there is to know about the interior of comets,” he said. A large comet might have enough rock in its core “to keep DNA material rather pristine and safe”, Gary said.
Radiation might be a problem for microbes, but not for very basic organic material, said Kevin Conod, an astronomer and manager of the Dreyfuss Planetarium at the Newark Museum.
“I think the theory of panspermia is not about microbes from space, but amino acids, the building blocks of life,” Conod said. “Radiation wouldn’t necessarily affect those enough to kill pieces of protein.”
The Rutgers researchers thawed five microbial samples taken from ice between 100,000 years and eight million years old, and were able to grow several organisms in liquid media, said Kay Bidle, a Rutgers marine microbiologist and oceanographer.
They also wanted to know how long organisms could live over extended geologic periods, Bidle said.
“This is of interest to whether there is life on Mars,” he said, as the site in Antarctica resembled icy regions on the Red Planet.
Microbes might survive a trip from Mars if encased in a meteorite, Falkowski of Rutgers said. “So we could all be Martians,” he said.
Theory about Atlas morphology (Saturn moon)
Authors: Enrique Ordaz Romay
(Submitted on 13 Aug 2007)
Abstract: On June 12, 2007 the Cassini probe sent the images of a small moon of Saturn called Atlas which is located between the ring A and the small ring R/2004 S 1. These images have shown that the Atlas morphology is very different from other moons of similar dimensions. In the present article we propose a reasonable theory, to that we denominated “flying dune”, that explains its morphologic characteristics from its magnitudes like mass, diameters and orbital radius, as well as its orbital position and the interpretation of the images caught by the Cassini probe.
Comments: 32 pages, 8 images, 2 tables, 4 figures and 5 graphs
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0708.1678v1 [astro-ph]
Submission history
From: Enrique Ordaz Romay [view email]
[v1] Mon, 13 Aug 2007 09:54:35 GMT (772kb)
http://arxiv.org/abs/0708.1678
Images of Saturn’s Small Moons Tell the Story of Their Origins
Imaging scientists on NASA’s Cassini mission are telling a tale of how the small moons orbiting near the outer rings of Saturn came to be. The moons began as leftover shards from larger bodies that broke apart and filled out their “figures” with the debris that made the rings.
It has long been suspected that Saturn’s rings formed in the disintegration of one or several large icy bodies, perhaps pre-existing moons, by giant impacts. The resulting debris quickly spread and settled into the equatorial plane to form a thin disk surrounding the planet. And the small, irregularly shaped ring-region moons were believed to be the leftover pieces from this breakup.
Now, several years’ worth of cosmic images of Saturn’s 14 known small moons have been used to derive the sizes and shapes of most of them, and in about half the cases, even masses and densities. This information, published in the Dec. 7 issue of the journal Science, has led to new insights into how some of these moons may have formed.
The tip-off was the very low density of the inner moons, about half that of pure water ice, and sizes and shapes that suggested they have grown by the accumulation of ring material. The trouble was, these moons are within and near the rings, where it is not possible for small particles to fuse together gravitationally. So how did they do it? They got a jump start.
“We think the only way these moons could have reached the sizes they are now, in the ring environment as we now know it to be, was to start off with a massive core to which the smaller, more porous ring particles could easily become bound,” said Carolyn Porco, Cassini imaging team leader from the Space Science Institute in Boulder, Colo. Porco is the lead author of the first of two related articles published in this week’s issue of Science.
Simple calculations and more complicated computer simulations have shown that ring particles will readily become bound to a larger seed having the density of water ice. By this process, a moon will grow even if it is relatively close to Saturn. The result is a ring-region moon about two to three times the size of its dense ice core, covered with a thick shell of porous, icy ring material. To make a 30-kilometer moon (19 miles) requires a seed of about 10 kilometers (6 miles).
Where did such large cores come from? And when did this all take place?
“The core may in fact be one of the remnants from the original ring-forming event,” said co-author Derek Richardson, professor of astronomy at the University of Maryland, College Park, “which might have been left intact all this time and protected from additional collisional breakup by the mantle of ring particles around it.”
Just exactly when the rings formed is not known. “But it is not out of the question that the moons date back to the time of ring formation,” said Porco.
The researchers show that the cores of Pan and Daphnis, which orbit within gaps in the outer A ring, were large enough to open narrow gaps. Accretion, or accumulation of material, they say, probably occurred quickly. The moons grew and their gaps widened, achieving their present sizes before the gaps were completely emptied of material, and probably before the local rings reached their present thickness.
So how did Pan in the main rings, and Atlas, which orbits just beyond the outer edge of the main rings, get the prominent equatorial ridges that make them look like flying saucers? The second paper reports evidence for a secondary stage of accretion that occurred after the moons’ growth was completed and after the rings flattened to their present 20-meter (66 feet) thickness.
“Our computer simulations show that the ridges must have accreted rapidly when Saturn’s rings were thin, forming small accretion disks around the equators of Pan and Atlas,” said Sebastien Charnoz, lead author and an associate of imaging team member Andre Brahic at the University Paris-Diderot and CEA Saclay, in France. “The ridges might be the remains of ‘fossilized’ accretion disks, fundamental structures seen at all scales in the universe, from planetary rings to galaxies.”
Images of Saturn’s small moons are available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini and http://ciclops.org.