The uncertainty of science: The geology of Vesta as seen by Dawn appears to contradict the present models for that asteroid’s origin.
The accumulated evidence from the Chelyabinsk meteorite now suggests the risk of large asteroid impacts might be ten times greater than previously estimated.
The Chelyabinsk asteroid had approached Earth from a region of the sky that is inaccessible to ground-based telescopes. In the 6 weeks before the impact, it would have been visible above the horizon only during the daytime, when the sky is too bright to see objects of its size, says Borovička.
“The residual impact risk — from asteroids with yet-unknown orbits — is shifting to small-sized objects,” says Peter Brown, a planetary scientist at the University of Western Ontario in London, Canada, and an author on the Nature papers.
Of the millions of estimated near-Earth asteroids 10–20 metres in diameter, only about 500 have been catalogued. Models suggest that an object the size of the Chelyabinsk asteroid hits Earth once every 150 years on average, Brown says. But the number of observed impacts exceeding 1 kiloton of TNT over the past 20 years alone hints at an actual impact risk that may be an order of magnitude larger than previously assumed,
The data also now suggests that the Chelyabinsk asteroid was twice as big as previously thought, and that it had an almost identical orbit to a much larger already known asteroid.
Students crash rockets into the ground on purpose! With video.
In what at first glance seems like a terrible sense of direction, in March students from the University of Washington fired rockets from kites and balloons at an altitude of 3,000 ft (914 m) straight into the ground at Black Rock, Nevada: a dry lake bed in the desert 100 mi (160 km) north of Reno. This may seem like the ultimate in larking about, but it’s actually a serious effort to develop new ways of collecting samples from asteroids.
Hayabusa 2 test fires its cannon in preparation for its 2014-2018 asteroid sample return mission.
A newly discovered half-mile wide asteroid has 1 in 63,000 chance of hitting the Earth in 2032.
That’s the Russian report above, which on these matters tend to be panic-stricken. Here’s the JPL version, which downplays the concern.
Divers working at a Russian lake have recovered a half-ton piece of the asteroid that exploded over Chelyabinsk on February 15.
Boom! A remotely operated Russian telescope, located in New Mexico, on Wednesday discovered a kilometer wide Near Earth asteroid.
The asteroid, believed to be the 704th largest with an orbit that comes relatively near Earth, does not pose a danger of crashing into our planet, said the head of the observatory that made the discovery. “It’s a big asteroid, but it poses no danger for us,” Leonid Elenin, who lives in the Moscow Region, told RIA Novosti on Friday.
Finding a new asteroid like this illustrates that there might be other such large objects out there undiscovered. Also cool is how the Russians discovered it, using equipment in the United States!
Posted from Midland, Texas, the center of the world for the American oil industry.
Astronomers have found evidence of the remains of an exoplanet that they think was once wet and rocky.
Using observations obtained with the Hubble Space Telescope and the large telescopes of the W. M. Keck Observatory , they found an excess of oxygen – a chemical signature that indicates that the debris had once been part of a bigger body originally composed of 26 per cent water by mass. By contrast, only approximately 0.023 per cent of the Earth’s mass is water.
From what I can gather, the actual data here is somewhat skimpy, requring a lot of assumptions for the scientists to come to this conclusion. Nonetheless, the data is interesting and very tantalizing.
Posted from Memphis, Tennessee.
Scientists in Egypt have found what they think is evidence of a comet impact from 28 million years ago.
The best part however is this:
At the centre of the attention of this team was a mysterious black pebble found years earlier by an Egyptian geologist in the area of the silica glass. After conducting highly sophisticated chemical analyses on this pebble, the authors came to the inescapable conclusion that it represented the very first known hand specimen of a comet nucleus, rather than simply an unusual type of meteorite.
Assuming this claim is confirmed it is a very significant discovery. As far as I know, no other specimens from a comet nucleus have been identified previously.
The asteroid that might hit the Earth in 2880.
Divers have pulled fragments from the February 15 Chelyabinsk meteorite impact out of nearby Chebarkul Lake.
Posted from Gaitlinburg, Tennessee, the Coney Island of the Smoky Mountains. The drive today was sadly a lot longer than planned, as we hit bad traffic in Nashville.
In a paper published today on the Los Alamos astro-ph preprint service, astronomers propose that as many as eleven past extinction events can be linked to the Sun’s passage through the spiral arms of the Milky Way. (You can download the paper here [pdf].)
A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy’s various spiral arms.
The figure on the right, from their paper, shows the Sun’s orbit in red over the last half billion years. The Sun’s present position is indicated by the yellow spot, and the eleven extinctions are indicated by the circles.
There are obviously a great deal of uncertainties in this conclusion. Most significantly, the shape and history of the Milky Way remains very much in doubt, especially since we reside within it and cannot really get a good look at it. Though in recent years astronomers have assembled a reasonable image of the galaxy’s shape — a barred spiral with two major arms and several minor ones — this picture includes many assumptions that could very easily be wrong.
Nonetheless, the paper’s conclusions are interesting.
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Using photos from Dawn astronomers have now assembled an online atlas of the asteroid Vesta that the public can explore.
NASA will reactivate the Wide-field Infrared Survey Explorer (WISE) next month to use it to look for more near Earth asteroids.
This decision raises two thoughts.
Engineers have identified twelve asteroids that could be captured with today’s technology.
Their number one most easily moved space rock is named 2006 RH120. A single rocket burn in 2021 would be enough to place this roughly 4-meter-wide asteroid into orbit around a Lagrange point by 2026. NASA could then launch people to study this object (which would barely be bigger than the astronauts themselves) and learn about its history.
An update on Dawn in its journey from the asteroids Vesta to Ceres. Bottom line:
Dawn is 18 million kilometers (11 million miles) from Vesta and 50 million kilometers (31 million miles) from Ceres. It is also 3.47 AU (519 million kilometers or 322 million miles) from Earth, or 1,310 times as far as the moon and 3.42 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 58 minutes to make the round trip.
Want to land on an asteroid? Watch out, a gentle touchdown might cause avalanches everywhere!
Radar images of asteroid 1998 QE2, flying past the Earth today, show that it has its own moon.
When astronomers analyzed radar readings to create their first maps of 1998 QE2, the big asteroid that’s due to sail past Earth on Friday, they were surprised to find that it has a moon twice as big as an ocean liner. 1998 QE2 itself is way bigger: The latest readings from NASA’s Deep Space Network antenna in Goldstone, Calif., are consistent with earlier estimates that the asteroid is about 1.7 miles (2.7 kilometers wide). But the moon is hefty as well. Astronomers estimate its diameter at 2,000 feet (600 meters).
Engineers now suspect that the shutdown of the GOES-13 weather satellite last week was caused by a micrometeorite hit.
They also think they will be able to get the satellite up and running again.
Tests have now shown that at least one bead of jewelry from an Egyptian tomb was made from a meteorite.
The tube-shaped bead is one of nine found in 1911 in a cemetery at Gerzeh, around 70 kilometres south of Cairo. The cache dates from around 3,300 BC, making the beads the oldest known iron artefacts in Egypt.
An early study found that the iron in the beads had a high nickel content — a signature of iron meteorites — and led to the suggestion that it was of celestial origin2. But scholars argued in the 1980s that accidental early smelting efforts could have led to nickel-enriched iron3, while a more recent analysis of oxidised material on the surface of the beads showed low nickel content4.
To settle the argument, Diane Johnson, a meteorite scientist at the Open University in Milton Keynes, UK, and her colleagues used scanning electron microscopy and computed tomography to analyze one of the beads on loan from the Manchester Museum, UK. The researchers weren’t able to cut the precious artefact open, but they found areas where the weathered material on the surface of the bead had fallen away, providing what Johnson describes as “little windows” to the preserved metal beneath.
The nickel content of this original metal was high — 30% — suggesting that it did indeed come from a meteorite. To confirm the result, the team observed a distinctive crystallographic structure called a Widmanstätten pattern. It is only found in iron meteorites, which cooled extremely slowly inside their parent asteroids as the Solar System was forming.
The asteroid is coming! The asteroid is coming!
The fly-by of the large asteroid 1998 QE2 tomorrow at about 5 pm (Eastern) is causing a lot of hype. It is interesting, but hardly the big news event NASA and others want to make it. The scientists will like it because they get another close look at an asteroid. Others are using it to hype up the threat of asteroids, though that threat is not changed in any way by this fly-by.
The impact of a 100 pound meteorite on the Moon in March produced the brightest flash ever recorded.
Anyone looking at the Moon at the moment of impact could have seen the explosion–no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.
Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the impact in a digital video recorded by one of the monitoring program’s 14-inch telescopes. “It jumped right out at me, it was so bright,” he recalls.
The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph. The resulting explosion1 packed as much punch as 5 tons of TNT.
It will be really interesting to see the Lunar Reconnaissance Orbiter images of the impact site, which can’t be taken until the spacecraft passes over the site and can photograph it.
Cassini has imaged meteorites as they crash into Saturn’s rings.
The sky isn’t falling: A detailed analysis of the tumbling of the asteroid Apophis, detected by radar observations in January, suggests it will be easier to predict the asteroid’s orbit in the future.
The gentle but persistent nudging [of the Yarkovsky effect] arises when sunlight is absorbed by a rotating object and then reradiated as heat in some other direction. In particular, if Apophis were spinning retrograde (opposite the way Earth does), then over time its orbit would change in a way that increases the chance of impact in 2036. But now we can rest easy, because Apophis appears to be tumbling as it orbits the Sun. That’s the conclusion reached by a team of telescopic observers who monitored the asteroid’s light curve as it passed near Earth in January. Apophis is spinning around two axes at the same time, implying that any Sun-warmed surfaces are radiating heat in all directions, not just one in particular.
It is very difficult to measure the Yarkovsky effect, thus making it very difficult to precisely calculate the orbits of many near Earth asteroids. In the case of Apophis, however, it appears the astronomers have gotten a good handle on the problem.
The uncertainty of science: Is this meteorite from Mercury? Some scientists now say no.
Was a meteorite found in Africa in 2012 originally from Mercury?
A new model of the origin of asteroids suggests that in the beginning they weren’t rubble piles but “churning balls of mud.”
Chicken Little Report: Four asteroids buzzed the Earth this past week.
I suspect that the increase in detected asteroids is not because there are more of them but because our ability to detect them continues to improve.
The search to find and understand the Chelyabinsk meteorite.
