29 July 2008

Harvest the Sun, Beam it Down

O. Glenn Smith was on NPR today talking about SBSP.
See http://www.nytimes.com/2008/07/23/opinion/23smith.html

16 July 2008

Asteroid cruises past Earth ... with a partner!

http://www.msnbc.msn.com/id/25677351/ By Robert Roy Britt Space.com updated 2:36 p.m. ET, Mon., July. 14, 2008

Good-sized asteroid sailing past our planet turns out to be two giant rocks

A good-sized asteroid sailing past our planet right now turns out to be two giant rocks doing a celestial jig.
The setup, catalogued as 2008 BT18, was thought to be nearly a half-mile wide after its discovery by MIT's LINEAR search program in January. Nothing else was known about it.
Now seen as two objects orbiting each other, the pair will be closest to Earth on today, at about 1.4 million miles (2 million kilometers) away. That's nearly six times as far from us as the moon.
It will not strike the planet. But scientists want to learn more about binary asteroids because one day they might find one headed our way. Deflecting a binary off course could be considerably more challenging that altering the path of a single rock.
Radar observations from the Arecibo Observatory in Puerto Rico on July 6 and 7 "clearly show two objects," said Lance Benner of NASA's Jet Propulsion Laboratory.
The objects are estimated to be 1,970 feet (600 meters) and 650 feet (200 meters) in diameter. The larger one rotates upon its axis in 3 hours or less.
Additional observations from NASA's Goldstone radar in the Mojave Desert in California are expected to reveal more about the density, shapes and orbit of the pair.
Asteroids are often loose rubble piles rather than solid objects, and pairs are common. Scientists announced earlier this month that binaries can be created when energy from sunlight splits a loose asteroid in two.
While most asteroids roam in a belt between Mars and Jupiter, some are kicked or drawn inward and cross our path around the sun. Some 15 percent of these near-Earth asteroids are binaries. But few come so close.
Asteroid 2008 BT18 remains classified by NASA as "potentially hazardous" because its future orbits have not been fully determined.
Asteroids are known to change course over time, and in fact one big boulder, named Apophis, will alter course significantly during a close Earth flyby in 2029. Earth's gravity will bend the rocks' trajectory around the sun. Depending on how that interaction plays out, Apophis has a minor chance of hitting the planet in 2036. Scientists expect the odds of impact to diminish or evaporate after the first flyby, however.

Killer asteroid predictions 'off by millions of miles'

http://www.newscientist.com/home.ns 15 July 2008David ShigaMagazine issue 2664
The solar system's most dangerous rock, Apophis, could be more of a threat to Earth than thought. YOU'D think that by now we'd have a firm grip on the trajectory of the solar system's most worrisome chunk of rock. In fact we have only a hazy understanding of how likely the asteroid Apophis is to strike Earth. What's more, budget cuts may shut down the telescope that could clarify the situation.
Since Apophis was discovered in 2004, asteroid-watchers have known that it has a slim chance of hitting Earth in 2036. At 270 metres wide, it is too small to rival the object that wiped out the dinosaurs, but it could cause devastating tsunamis were it to hit the ocean. Worrying as this is, we have been able to take comfort in the computed probability of impact, which is just 1 in 45,000.
Now it seems the true risk is unclear, thanks to minute effects that the calculations didn't take into account.

Maybe Chicken Little Wasn’t Paranoid After All

From: http://www.nytimes.com/2008/07/06/weekinreview/06revkin.html?ref=scienceJuly 6,
THE Earth is pockmarked with the evidence of ancient collisions — huge craters blasted into its surface by asteroids or comets. One such object, striking 65 million years ago in the Yucat√°n in Mexico, is believed by some experts to be linked to the demise of the dinosaurs.
For a decade, NASA has been busy trying to identify what else is headed this way, particularly those potential “civilization killers” of 1 kilometer (.62 miles) or more in diameter that have orbits coming within 30 million miles of the Earth’s — too close for comfort by space standards.
But the big ones are, in many ways, the easy part. Smaller rocks matter, too. Perhaps nowhere is that so evident as in central Siberia, where 100 years ago last week, something — presumably a meteoroid, most experts say — streaked across the sky and exploded at an estimated height of 28,000 feet with a force equivalent to 185 Hiroshima bombs, leveling some 800 square miles of forest. Simulations by the Sandia National Laboratories showed that object could have been just 90 feet across.
The explosion that lit up the Siberian sky in a fireball shortly after 7 a.m. on June 30, 1908, is known as the Tunguska event, after the river the flows through the damage zone, and is widely considered the modern-day warning about the dangers slinging through space.
NASA’s Jet Propulsion Laboratory in Pasadena, Calif., has estimated that a Tunguska-size asteroid will enter Earth’s atmosphere once every 300 years and says there may be 375,000 objects of such size out there.
Fortunately, the odds are good that the next one will fall over one of our oceans, which take up more than two-thirds of the Earth’s surface, or the planet’s still-vast stretches of uninhabited lands. How much in taxpayer dollars should be invested to pinpoint such hazards is one of the toughest risk-management exercises around.
Donald K. Yeomans, who manages the jet propulsion lab’s Near-Earth Object Program, said the Earth’s atmosphere is continually streaked by space stuff, ranging from the basketball-size (several a day) to the Volkswagen-size (twice a year). Almost everything burns up, though some may explode in the air, a phenomenon known as an airburst, with the potential of causing damage below. And then there are objects, like the meteorite that dug a 60-foot-wide crater in Peru last September. Perhaps no bigger than a basketball, the meteorite was a reminder of the destructive power of what is lurking out there.
“In fact, there was a daylight fireball event widely observed near Los Angeles two days ago,” Dr. Yeomans said in an e-mail message last Thursday. “I take these events as Mother Nature’s little reminders that we need to pay attention, find and track the large ones and then deflect the very few that threaten us. Tunguska was another reminder. Until recently, we humans did not pay heed to these shots across the bow but now, I think, there is more of a recognition of this low probability — but high consequence — type of event.”
NASA estimates that there are about 940 or so near-Earth space rocks a kilometer in diameter or larger. So far, according to Dr. Yeomans, NASA has identified 743. (Overall, NASA has pinpointed more than 5,500 near-Earth objects.)
Budget constraints have slowed NASA’s efforts to meet its goal of identifying 90 percent of those big objects by next year. As for rocks similar in size to the one that exploded over Siberia, a NASA search is probably a long way down the line.
Even so, one way or the other, many more potential incoming asteroids will be identified in the next decade, astronomers say. But awareness is just the first stage of grappling with the challenge, said Rusty Schweickart, the Apollo 9 astronaut who heads a foundation advocating more research on identifying near-Earth objects and developing unmanned spacecraft that could nudge them off track like a tugboat.
Mr. Schweickart said progress so far had come through constant pushing against resistant bureaucracies and politicians focused on whatever is the issue of the moment. And he said there was still no significant effort to devise an international agreement, let alone a deflection technique, for dealing with the inevitable earthbound asteroid or comet, large or small, when it is identified.
“It may be subtle,” he said, “but failure of the international decision process is the most likely reason that we’ll take a hit in the future.”

Hot super-Earths could support life, study indicates.

New Scientist <http://links.mkt751.com/ctt?kn=5&m=1942320&r=MTU4OTU3MDEyMAS2&b=0&j=OTU5OTkyMTkS1&mt=1> (7/11, Than) reported, "Massive, rocky worlds called 'super-Earths' -- even those orbiting searingly close to their stars -- may provide the right conditions for life," according to researchers. According to Lisa Kaltenegger of the Harvard-Smithsonian Center for Astrophysics, "new models show that if a tidally locked super-Earth has an atmosphere at least as dense as Earth's, strong winds could transport heat from its hot side to its cold side," as could a global ocean. Previously it had been thought that "the atmospheres of such worlds would quickly vanish, as water vapor and other atmospheric molecules on the planet's dark side would turn to ice and plunge to the ground." The new finding "means super-Earths could potentially host life as close as 0.05 astronomical units away from dim stars known as red dwarfs, which make up about 85 percent of the stars in the galaxy." Further, some experts say, "super-Earths might even be more likely to support life than their Earth-sized cousins" as they would likely "experience more plate tectonic activity," which is seen as "necessary for life."