Tag: asteroids

Bad news for climate modelers

12:20 pm

A new analysis of the orbits of Ceres and Vesta says that in a surprisingly short time those orbits become chaotic and therefore unpredictable. More significantly, those orbits interact with the Earth’s and also make its long term orbit chaotic and unpredictable. From the abstract:

Although small, Ceres and Vesta gravitationally interact together and with the other planets of the Solar System. Because of these interactions, they are continuously pulled or pushed slightly out of their initial orbit. Calculations show that, after some time, these effects do not average out. Consequently, the bodies leave their initial orbits and, more importantly, their orbits are chaotic, meaning that we cannot predict their positions. The two bodies also have a significant probability of impacting each other, estimated at 0.2% per billion year. Last but not least, Ceres and Vesta gravitationally interact with the Earth, whose orbit also becomes unpredictable after only 60 million years. This means that the Earth’s eccentricity, which affects the large climatic variations on its surface, cannot be traced back more than 60 million years ago. This is indeed bad news for Paleoclimate studies. [emphasis mine]

The scientists found that it became impossible to calculate the orbits of the two largest asteroids after only several ten thousand years. They also found that “numerous asteroids in the main belt will behave in the same way with . . . much more chaotic behavior than previously thought.” Worse, the possibility of collisions was far higher than ever thought. Ceres and Vesta have a 1 in 500 chance of colliding with each other every billion years, while other asteroids have chances as low as 1 in 1000.

The importance of this discovery, which still needs to be confirmed by other researchers, cannot be understated.
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Another fuzzy Dawn image?

12:11 pm

July 9 Vesta image

Another image of Vesta from Dawn has been released. This image was taken on July 9 from a distance of 26,000 miles away. It is definitely an improvement over the previous image, with more small details becoming visible. However, I once again wonder about the softness of the image. Look at the limb of the planet. It is soft against the black sky. This is not what one would expect from perfectly focused camera.

Dawn goes into orbit around Vesta next week. We sure learn then for sure if there is a problem with its camera, or whether I am merely being a bit too nervous.

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A new image of Vesta from Dawn

2:36 am

Dawn continues to approach the large asteroid Vesta. Below is an image taken July 1st from about 62,000 miles. The image has a resolution of 5.8 miles per pixel.

Despite Vesta’s large size, 330 miles in diameter, it is nonspherical. This fact, combined with data that says it is differentiated with a core and mantle, suggests that it is the remains of a larger object that subsequently broke up.

Vesta from 62,000 miles

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Infrasonic detection of a near-Earth object impact over Indonesia on 8 October 2009

10:38 pm

From a paper published on Saturday in Geophysical Research Letters, scientists describe the after the fact detection of the impact of a near-Earth object about 6 to 10 yards in diameter over Indonesia in 2009. From the abstract:

We present analysis of infrasonic signals produced by a large Earth-impacting fireball, believed to be among the most energetic instrumentally recorded during the last century that occurred on 8 October, 2009 over Indonesia. This extraordinary event, detected by 17 infrasonic stations of the global International Monitoring Network, generated stratospherically ducted infrasound returns at distances up to 17 500 km, the greatest range at which infrasound from a fireball has been detected since the 1908 Tunguska explosion. From these infrasonic records, we find the total source energy for this bolide as 8–67 kilotons of TNT equivalent explosive yield, with the favored best estimate near ∼50 kt. Global impact events of such energy are expected only once per decade and study of their impact effects can provide insight into the impactor threshold levels for ground damage and climate perturbations.

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Asteroid sample return mission on slate for 2016

11:13 pm

Asteroid sample return mission on slate for NASA in 2016. The asteroid chosen in 1999 RQ36, which is significant.

The space rock has been classified as a potentially hazardous asteroid, since its orbit brings it close to Earth in the year 2182. There is an extremely remote chance (a recent study pegs it at about 1-in-1000) that the 1,900-foot-wide (579-meter) asteroid could pose a threat to Earth.

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Want to go to an asteroid?

9:38 am

A paper published today on the Los Alamos astro-ph preprint website has taken a close look at identifying the best nearby asteroids ideal for mounting a manned mission. The conclusion: our survey of such asteroids is very incomplete (only 65 known), and due to their location in Earthlike orbits they are very difficult to study.

Ultra-low delta-v NEOs are not readily found. Their closely Earth-like orbits mean that most of the time they are in the daytime sky, as seen from the Earth, and so are effectively undetectable. As they approach within <1AU of the Earth they start to lie near quadrature, and so come into the dawn or dusk sky on Earth. The strong scattered sunlight background makes optical surveys toward the dawn or dusk much less sensitive and, in practice, surveys do not look in these directions, preferring to observe where the sky is dark, within 45 degrees, and at most 60 degrees, of the anti-Sun, opposition, direction. As a consequence the lowest delta-v NEOs are undercounted by current surveys, and the factor by which they are undercounted is not yet known.

The paper proposes building a dedicated unmanned infrared mission and placing it in a Venus-like orbit where it would be better placed to see these difficult but important objects.

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The strange egg-shaped dwarf planet Haumea is apparently also covered with ice

8:35 pm

Truly alien: The strange egg-shaped dwarf planet Haumea is apparently also covered with crystallised ice.

“Since solar radiation constantly destroys the crystalline structure of ice on the surface, energy sources are required to keep it organized. The two that we have taken into consideration are that able to generate radiogenic elements (potassium-40, thorium-232 and uranium-238) from the inside, and the tidal forces between Haumea and its satellites,” [explained] Benoit Carry, co-author of the study and a researcher at the ESAC Centre of the European Space Agency (ESA) in Madrid (Spain).

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More info on the asteroid “flyby” of Earth this coming November 8

4:22 pm

More information on the asteroid “flyby” of Earth this coming November 8.

“On November 8, asteroid 2005 YU55 will fly past Earth and at its closest approach point will be about 325,000 kilometers [201,700 miles] away,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. “This asteroid is about 400 meters [1,300 feet] wide – the largest space rock we have identified that will come this close until 2028.”

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Newly discovered asteroid orbits in union with Earth

10:14 am

Newly discovered asteroid follows the Earth as it orbits the Sun, and has been doing it for a quarter million years.

Currently, three other horseshoe companions of the Earth are known to exist but, unlike 2010 SO16, these linger for a few thousand years at most before moving on to different orbits. Also, with an estimated diameter of 200–400 metres, 2010 SO16 is by far the largest of Earth’s horseshoe asteroids. The team has already used the Las Cumbres Observatory’s Faulkes Telescope in an on-going campaign to track the object and refine its orbit further. “It is not that difficult to spot with a medium-sized professional telescope”, says Dr Asher. “It will remain as an evening object in Earth’s skies for many years to come.”

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When is an Asteroid Not an Asteroid?

10:32 pm

When is an asteroid not an asteroid?

The layered structure of Vesta (core, mantle and crust) is the key trait that makes Vesta more like planets such as Earth, Venus and Mars than the other asteroids, McCord said. Like the planets, Vesta had sufficient radioactive material inside when it coalesced, releasing heat that melted rock and enabled lighter layers to float to the outside. Scientists call this process differentiation.

This question immediately demonstrates once again the terrible mess the International Astronautical Union made when it decided several years ago to define what makes a planet, and came up with a definition that simply doesn’t work. For if Vesta should be considered a planet, why not Pluto?

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Quarter-mile diameter asteroid to pass only 200,000 miles from the Earth on November 8, 2011

2:06 pm

Get those telescopes out! A asteroid, a quarter-mile in diameter, is going to pass only 200,000 miles from the Earth on November 8, 2011. Key quote:

Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an Earth collision over at least the next 100 years. However, this will be the closest approach to date by an object this large that we know about in advance and an event of this type.

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First results from the Hayabusa asteroid samples

3:52 pm

First results from the Hayabusa asteroid samples.

A preliminary analysis of asteroid samples returned last year by Japan’s Hayabusa probe show evidence the dust grains have a similar composition to stony meteorites that commonly fall to Earth. . . . The initial research also shows the samples inspected so far contain no organic molecules. Scientists also say the analysis confirms the rocks at Itokawa were formed 4.6 billion years ago at the dawn of the solar system.

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