Tag: asteroids

Scientists in Egypt have found what they think is evidence of a comet impact from 28 million years ago.

10:39 am

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.

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Linking mass extinctions to the Sun’s journey in the Milky Way

12:53 pm

The Sun's orbit in the Milky Way

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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NASA will reactivate the Wide-field Infrared Survey Explorer (WISE) next month to use it to look for more near Earth asteroids.

4:48 pm

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.

  • Why did they shut it down in the first place if it was still viable and could still do important research? If the cost wasn’t worth the benefit then, how has this equation changed now? And if the cost was worth the benefit, it then was foolish to shut it down in the first place. Though it costs money to operate these things, it is always cheaper to keep something running than to build something new. The press announcement above doesn’t really address these issues, and I wish it did.
  • I wonder if this decision is somehow related to the end of the Kepler mission. With Kepler out of service, maybe NASA decided to shift the funds to run that telescope over to WISE. They do not say, but the timing is interesting. This decision could be a hint that Kepler doesn’t really have another mission it can fulfill, and thus the money to run it has already been put elsewhere.
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Engineers have identified twelve asteroids that could be captured with today’s technology.

12:07 pm

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.

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An update on Dawn in its journey from the asteroids Vesta to Ceres.

9:30 am

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.

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Radar images of asteroid 1998 QE2, flying past the Earth today, show that it has its own moon.

9:05 am

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).

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Tests have now shown that at least one bead from an Egyptian tomb was made from a meteorite.

7:44 pm

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.

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The asteroid is coming! The asteroid is coming!

4:35 pm

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.

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The impact of a 100 pound meteorite on the Moon in March produced the brightest flash ever recorded.

9:45 am

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.

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An 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.

10:15 am

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.

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New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

10:32 pm

New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

Recent observations from Pan-STARRS PS1 telescope at Haleakala, Hawaii have reduced the current orbital uncertainty by a factor of 5, and radar observations in early 2013 from Goldstone and Arecibo will further improve the knowledge of Apophis’ current position. However, the current knowledge is now precise enough that the uncertainty in predicting the position in 2029 is completely dominated by the so-called Yarkovsky effect, a subtle nongravitational perturbation due to thermal re-radiation of solar energy absorbed by the asteroid. The Yarkovsky effect depends on the asteroid’s size, mass, thermal properties, and critically on the orientation of the asteroid’s spin axis, which is currently unknown. This means that predictions for the 2029 Earth encounter will not improve significantly until these physical and spin characteristics are better determined.

The new report, which does not make use of the 2013 radar measurements, identifies over a dozen keyholes that fall within the range of possible 2029 encounter distances. Notably, the potential impact in 2036 that had previously held the highest probability has been effectively ruled out since its probability has fallen to well below one chance in one million. Indeed only one of the potential impacts has a probability of impact greater than 1-in-a-million; there is a 2-meter wide keyhole that leads to an impact in 2068, with impact odds of about 2.3 in a million.

The second paragraph basically says that the keyholes that might bring Apophis back to Earth are very small, making it unlikely that the asteroid will fly through any one of them in 2029. The first paragraph however notes that it will be impossible to chart the asteroid’s course accurately enough to rule out this possibility until we have more data on the asteroid itself.

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Scientists have released some results from their look at asteroid 2012 DA14 during its fly-by last week.

8:37 am

Scientists have released some results, including video, from their look at asteroid 2012 DA14 during its fly-by last week. Key quote:

The asteroid’s path was perturbed by Earth’s gravitational field in such a way that it won’t come as close in the foreseeable future.

The video, which I have embeded below the fold, was produced from radar data. It clearly shows the asteroid’s rotation.
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Largest in a century.

9:58 am

More on today’s Russian meteorite: Largest in a century.

My earlier skepticism appears incorrect. This impact actually happened.

Note the article’s sense of outrage and panic that we aren’t looking for these types of rocks:

Although a network of telescopes watches for asteroids that might strike Earth, it is geared towards spotting larger objects — between 100 metres and a kilometre in size. “Objects like that are nearly impossible to see until a day or two before impact,” says Timothy Spahr, Director of the Minor Planet Center in Cambridge, Massachusetts, which tracks asteroids and small bodies. So far as he knows, he says, his centre also failed to spot the approaching rock.

Yet, today’s impact actually illustrates the wisdom of excluding this kind of small asteroid from searches. They aren’t big enough to do serious harm, and trying to find them would hamper searches for larger asteroids that do pose a serious risk.

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