Tag Archives: impact

Largest ancient meteorite impact found?

The uncertainty of science: Scientists doing geothermal research in Australia have discovered evidence of what they think is the largest known impact zone from an meteorite on Earth.

The zone is thought to be about 250 miles across, and suggests the bolide split in two pieces each about 6 miles across before impact. The uncertainty is that the evidence for this impact is quite tentative:

The exact date of the impacts remains unclear. The surrounding rocks are 300 to 600 million years old, but evidence of the type left by other meteorite strikes is lacking. For example, a large meteorite strike 66 million years ago sent up a plume of ash which is found as a layer of sediment in rocks around the world. The plume is thought to have led to the extinction of a large proportion of the life on the planet, including many dinosaur species.

However, a similar layer has not been found in sediments around 300 million years old, Dr Glikson said. “It’s a mystery – we can’t find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” he said.

In other words, they find some evidence that an impact occurred, but not other evidence that is expected to be found with such an impact. Moreover, the rocks at the sedimentary layer where the impact is found are dated around 300 million years ago, a time when no major extinction took place. Either this impact didn’t really happen, or it didn’t happen when it appears it should have, or it shows that large impacts don’t necessarily cause mass extinctions.

A 100-foot diameter newly discovered asteroid will zip past the Earth inside the Moon’s orbit today at 4:07 pm Eastern.

Chicken Little report: A 100-foot diameter newly discovered asteroid will zip past the Earth inside the Moon’s orbit today at 4:07 pm Eastern.

The asteroid, dubbed 2014 DX 110, is about 100 feet in diameter and is set to come within 216,000 miles of Earth — a close shave by astronomical standards, considering our Moon orbits the Earth at a distance of about 238,900 miles.

While an object that size may not seem imposing, if it were to strike the Earth, it would release a devastating amount of energy greater than a nuclear weapon. The infamous asteroid that exploded over Tunguska, Siberia, on June 30, 1908, has been estimated to be about 30 meters to 60 meters — 100 feet to 200 feet — in diameter.

While it is true that the impact would be significant, this news report does the typical fear-mongering to make the story seem interesting. The problem, however, is that the detection of these fly-bys is becoming more frequent. The number of asteroids isn’t changing, but our ability to spot them is, and with more frequent discoveries comes more frequent news stories like this. I fear that such stories — fueled by press releases from various astronomy organizations — are going to begin to sound like a kid “crying wolf” to the general public. The threat from an asteroid impact is real, even if most asteroids miss us. Desensitizing the public to the threat is not a good thing.

A September asteroid impact on the Moon captured by Spanish astronomers.

A September asteroid impact on the Moon captured as it happened by Spanish astronomers.

On 11 September 2013, Prof Jose M. Madiedo was operating two telescopes in the south of Spain that were searching for these impact events. At 2007 GMT he witnessed an unusually long and bright flash in Mare Nubium, an ancient lava-filled basin with a darker appearance than its surroundings. The flash was the result of a rock crashing into the lunar surface and was briefly almost as bright as the familiar Pole Star, meaning that anyone on Earth who was lucky enough to be looking at the Moon at that moment would have been able to see it. In the video recording made by Prof Madiedo, an afterglow remained visible for a further eight seconds. The September event is the longest and brightest confirmed impact flash ever observed on the Moon.

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

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.

A new chemical analysis of lunar rocks from the Apollo missions has cast doubt on the theory that the Moon was formed when the Earth was hit by a Mars-sized object about 4.5 billion years ago.

The uncertainty of science: A new chemical analysis of lunar rocks from the Apollo missions has cast doubt on the consensus theory that the Moon was formed when the Earth was hit by a Mars-sized object about 4.5 billion years ago.

The orbit of a 150 foot wide asteroid that zipped past the Earth in February, has an orbit so much like the Earth’s that astronomer’s expect it back next year.

Duck! The orbit of a 150 foot wide asteroid that zipped past the Earth in February, has an orbit that will bring it past the Earth again on February 15, 2013 by less than 15,000 miles.

The team use several automated telescopes to scan the sky, and the discovery came somewhat serendipitously after they decided to search areas of the sky where asteroids are not usually seen. “A preliminary orbit calculation shows that 2012 DA14 has a very Earth-like orbit with a period of 366.24 days, just one more day than our terrestrial year, and it ‘jumps’ inside and outside of the path of Earth two times per year,” says Jaime.

While an impact with Earth has been ruled out on the asteroid’s next visit, astronomers will use that close approach for more studies and calculate the Earth and Moon’s gravitational effects on it.

Because this newly discovered asteroid passes so close and frequently to both the Earth and Moon, astronomers will need a lot more data before they can pin down its orbit precisely, and thus predict the chances of a collision in the near future.

JPL has issued a press release “reality check” on the impact possibilities of asteroid 2011 AG5 in 2040.

JPL has issued a press release “reality check” on the impact possibilities of asteroid 2011 AG5 in 2040.

“In September 2013, we have the opportunity to make additional observations of 2011 AG5 when it comes within 91 million miles (147 million kilometers) of Earth,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. “It will be an opportunity to observe this space rock and further refine its orbit. Because of the extreme rarity of an impact by a near-Earth asteroid of this size, I fully expect we will be able to significantly reduce or rule out entirely any impact probability for the foreseeable future.” Even better observations will be possible in late 2015.

In other words, we really will not know anything more about these possibilities until late next year.

Astronomers have discovered a five hundred foot wide asteroid that has a 1 in 600 chance of hitting the Earth in 2040.

Astronomers have discovered a five hundred foot wide asteroid that has a 1 in 600 chance of hitting the Earth in 2040.

“2011 AG5 is the object which currently has the highest chance of impacting the Earth … in 2040. However, we have only observed it for about half an orbit, thus the confidence in these calculations is still not very high,” said Detlef Koschny of the European Space Agency’s Solar System Missions Division in Noordwijk, The Netherlands.

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

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.