- Titan Raises Tsunamis in Saturn’s Ring
- Idaho’s Sand Dunes Tell Ancient Climate Story
- Test-Tube Baby Innovator Grabs Nobel Prize
- Why Can’t We Be Friends? Top 10 Interspecies BFF Videos
- Mutant Worms Produce Piles of Spider Silk
Posted: 04 Oct 2010 03:19 PM PDT
A crack in one of Saturn's rings could be held open by the planet's largest moon, Titan. A new analysis of data from the Cassini orbiter shows that Titan's gravity lifts part of the ring in a rotating tidal wave almost two miles high.
"It's a little bit like a tsunami propagating away from an earthquake fault," said planetary scientist Phillip Nicholson of Cornell University in a press briefing October 4. Nicholson presented a new model explaining the ring gap at the American Astronomical Society's Division for Planetary Sciences meeting in Pasadena, California.
Saturn's rings are riddled with gaps, many of which are held open by small moons. But in the last five years, since Cassini discovered the moon Daphnis, no new moons have shown up in the other known fissures.
"It's become an increasing problem, as to what determines where these gaps are in the rings and what keeps the gaps open," Nicholson said.
One such gap has been a mystery since the Voyager 1 spacecraft flew by Saturn in the 1980s. Using radio observations, Voyager detected what looked like a 9-mile-wide gap in the middle of Saturn's C ring. Just outside the gap, astronomers saw a wave-like structure circling the ring, which they interpreted as an extra-clumpy region pushing through the ring's flat disk.
But Cassini found the gap to be much narrower, only about a mile and a half wide. Even weirder, the gap seemed to disappear about half the time.
Both puzzles can be resolved by thinking of the ring in three dimensions, Nicholson says. Last year, the angle of sunlight during Saturn's spring equinox revealed that many of Saturn's rings have mountains.
"Mostly the rings are very flat. It's the most two-dimensional structure we know in the universe," Nicholson said. "But there are exceptions to every rule, and there are exceptions to the rule that Saturn's rings are flat everywhere."
The new model suggests the actual gap in the ring is only about a third of a mile wide, but part of the ring rises 2 miles in the air. The crack looked wider to Voyager than to Cassini because of the angles each spacecraft was observing from.
"In hindsight, what looked like a 15-kilometer-wide gap actually was this gap with a vertical displacement of about 3 kilometers (1.8 miles), projected and seen almost edge on," Nicholson said. "If we assume this was vertical and not horizontal and do the projection, it fits perfectly with this model, better than you have any right to expect."
The ring's corrugation comes from a gravitational relationship with Titan, whose orbit around Saturn falls at a slight angle to the ring plane. At a certain point in its orbit, Titan yanks the ring particles upward, starting a wave that travels around the ring.
"The whole pattern rotates around at the same rate as the satellite Titan orbits Saturn, once every 16 days," Nicholson said. The wave rolling along under Cassini occasionally blocked the spacecraft's view. "That accounts for the fact that the gap seems to come and go," he added.
This sort of wave could explain some of the other gaps in Saturn's rings that are not held open by moons, although it could also be unique to Titan and the C ring, Nicholson said.
"This and some other work suggests there might not be one explanation for gaps, there may be 3 or 4 or even more different dynamical circumstances that can give rise to these gaps."
The insights gleaned from Saturn's rings can be applied to disks all over the galaxy, including disks around stars that will eventually coalesce into planets, added Linda Spilker, Cassini deputy project scientist at the Jet Propulsion Laboratory.
"Saturn really is a wonderful, natural lab for understanding how the protoplanetary nebula might have evolved," she said.
Images: 1) Cassini's view of Saturn shortly after the spring equinox in August, 2009. NASA/JPL/SSI 2) NASA/JPL/Cornell
Posted: 04 Oct 2010 12:13 PM PDT
From the ground, in an everyday rush, it's easy to forget that the landscapes beneath our civilization are part of an epic geological narrative. But through the perspective-altering intervention of satellite imagery, that narrative is revealed, as in this photograph of sand dunes in Idaho's Snake River valley.
The dunes were formed 10,000 years ago, when the last Ice Age ended and what is now eastern Idaho warmed, causing lakes to shrink and exposing sediments carried aloft by wind until hitting a line of extinct volcanoes. The sands accumulated at their base, forming crescent-shaped dunes with tips pointing in the ancient wind's direction.
Taken by NASA's EO-1 satellite, the photograph underscores what's so marvelous about both geology and Earth imagery from space: They expand consciousness in time.
"A sense of time is the most important thing to get across to a non-geologist," said tectonicist Eldridge Moores of the University of California, Davis in John McPhee's Assembling California. "A million years is a small number on the geological time scale, while human experience is truly fleeting — all human experience, from its beginning, not just one timeline."
Posted: 04 Oct 2010 10:44 AM PDT
The 2010 Nobel Prize in physiology or medicine goes to British researcher Robert Edwards for pioneering in vitro fertilization, or IVF, a process that has led to roughly 4 million births since it was first successfully done in 1978.
Human IVF treats infertility caused when sperm and egg fail to meet within a prospective mother. A woman undergoing IVF is stimulated with hormones to produce eggs, and multiple eggs are removed from her ovaries and fertilized with sperm from a donor. Healthy fertilized eggs, or embryos, are transferred back into the woman's uterus. When successful, a pregnancy ensues.
Edwards began research on IVF in the 1950s and later worked with gynecologist Patrick Steptoe in refining the process of egg removal, fertilization and reimplantation. Early work had shown this could be done in rabbits. In the late 1960s, Edwards was the first to try human-egg removal and fertilization in vitro, a Latin term meaning "in the glass." Ultimately, this gave rise to a now outdated term, test-tube babies.
Edwards and Steptoe researched IVF at the University of Cambridge and at hospitals in Oldham, England, where Steptoe worked. Edwards also collaborated with scientists internationally. But a decade would pass before the first IVF success, a baby born in Oldham in 1978 following a full-term pregnancy. Edwards established an IVF research center in Cambridge.
Steptoe died in 1988. The Nobel committee doesn't award prizes posthumously. In granting Edwards the prize, the Nobel committee cited IVF as a "milestone" in medical care. IVF complications are very rare, but the procedure succeeds in only 25 to 30 percent of attempts, causing emotional and financial hardship for many couples. New findings might make predicting success better for those who have failed one attempt and are considering another.
Edwards previously won the Lasker award for his work. Edwards "was a man much ahead of his time not just in IVF, but in pre-implantation genetic diagnosis, the derivation of embryonic stem cells and also for his publications and lectures on ethics in science and the role of regulation," says Martin Johnson, a reproductive sciences expert at the University of Cambridge.
The prize is worth about $1.5 million.
Image: Niels Geijsen, Massachusetts General Hospital/National Science Foundation
Posted: 04 Oct 2010 04:00 AM PDT
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What is it about interspecies friendship that makes it universally cute, hilarious and heartwarming?
I don't know the answer, but if you tell me there is something better on the internet, I won't believe you. These videos of friendship between a tortoise and a hippo, a gorilla and a kitten, and an elephant and a dog are all the evidence I need.
There are some interesting similarities among many of the videos. Many involve domesticated animals, not only dogs and cats, but apes, elephants and pigs. Many also result from freak accidents, like a tsunami that washed the baby hippo to shore, where it was raised by the tortoise. Or the baby squirrel that fell out of the tree, was rescued, and raised by a mother cat.
Many of these animals seem confused about their identity. My guess is the hippo thinks he's a tortoise, the baby squirrel thinks he's a kitten (it even learns to purr).
In the case of Koko the gorilla and her baby kitten, All Ball, it seems more likely that Koko is displaying the ability to care for and become friends with a pet just like we do. It's unclear if All Ball thinks he's a gorilla.
These apparent friendships raise all sorts of questions about how animals identify themselves and the apparent universality of certain emotions among humans, mammals and tortoises.
If you know of other examples that should be included, please let us know. We can't get enough.
Posted: 04 Oct 2010 04:00 AM PDT
Snippets of spider genes let mutant silkworms spin silk stronger than steel. Scientists have coaxed miles of spider-like silk from a colony of transgenic silkworms, opening the door for large-scale production of super-strong, tough and flexible fibers.
"We can make a lot more silk from the silkworm process than you could possibly make from spiders," said molecular biologist Malcolm Fraser of the University of Notre Dame.
Spider silk has long been hailed as a superfiber, useful for everything from surgical sutures to bulletproof vests to scaffolding for growing cartilage. But spiders tend to be predatory loners who turn to cannibalism when raised in close quarters, making it nearly impossible to mass produce the treasured threads. A tapestry on display at the American Museum of Natural History last year took more than a million spiders to produce.
So scientists have tried to pull spider silk from tobacco plants, bacteria and even goats, with mixed success. Silkworms, on the other hand, are natural silk-spinning factories. A worm's silk gland takes up about a third of its entire body, Fraser said, and a single cocoon can yield a thread up to a mile long. Silkworms have been domesticated for centuries and are already used for making mass quantities of marketable silk.
By inserting specific spider genes into silkworm chromosomes, Fraser and his colleagues grew a colony of caterpillars that produce threads nearly as strong as spider silk.
"We can now make proteins that have the properties of spider silks in a commercializable platform," Fraser said. Fraser and his collaborators, including biochemist Randy Lewis of the University of Wyoming and Kim Thompson of Kraig Labs, presented the results in a press conference on the Notre Dame campus Sept. 29.
To create the mutant spinners, Fraser and his colleagues used a movable sequence of DNA called the piggyBac transposon to insert snips of spider genes into silkworm embryos. The resulting silk has different properties depending on where in the silkworm chromosome the spider DNA ends up.
"This manipulation allows us to custom build the threads to desired levels of flexibility, tensile strength and toughness," Fraser said.
Not all the embryos ended up expressing the spider DNA, however. To make sure they knew which worms were transgenic, the researchers attached a gene for red fluorescent protein to the spider DNA, ensuring all the mutants had glowing red eyes. The researchers then bred those caterpillars to raise a stable colony of spider-silk-spinning silkworms.
The resulting thread is actually a hybrid of specially engineered spider silk and natural silkworm silk. Even though they don't use "straight-up spider silk" — which wouldn't bond well with the silkworm proteins — the resulting strands are 80 percent as strong, Fraser said. The combination of their strength and flexibility, which materials scientists call toughness, approaches that of Kevlar.
In the wild, some spiders' silk can be up to 10 times tougher than Kevlar. A spider recently discovered in Madagascar spins threads tougher than any known biological substance.
"We haven't gotten a hold of that sequence yet, but you can bet that's going to be something we're going to engineer into our silkworms," Fraser said.
The researchers attached another fluorescent protein to the spider genes to make the silk itself glow green. The silk was just as strong, tough and flexible as before, indicating that scientists could attach other genes without diminishing the quality of the silk. One potential application of this feature is making bandages that stimulate the growth of regular skin instead of scar tissue.
"We can basically mix and match spider silk genes," Fraser said. "It's like mixing paint — take properties that you want and mix them in, the silkworm has them all expressed and you have a mixture of properties in your silk strand."
"I think it's a big step forward," said biomedical engineer David Kaplan of Tufts University. Until a scientific paper is published, he notes, there's no way to know how important or useful the silk will prove. But "the principle is very nice," he said. "I'm anxious to see more."
Images: University of Notre Dame
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