The origin of the Moon's Craters

A Hubble image of the asteroid Vesta. A new paper on the origins of the Moon's craters proposes that asteroids from the neighbourhood of Mars, some as large as Vesta, could have been responsible. Credit: NASA/Hubble

Moon's craters, together with samples of the surface returned during the Apollo program, tell the story of impacts from two different populations of small bodies.

The first rocky collection was gradually depleted over time: About 3.85 billion years ago (the Moon formed about 4.5 billion years ago) there was a cataclysmic heavy bombardment of material onto the surface that lasted only a few hundred million years.

The second collection of bodies appears not to have been depleted, however, and their impacts have continued at a steady pace. We observe this latter group today as Earth-orbit-crossing objects, and their numbers are apparently renewed at about the same rate that they are lost.

All these details are important to our understanding of the Moon, the history of the bombardment of the Earth by the same populations of asteroids, and - not least - to a better understanding of how the solar system evolved and thus how planetary systems around other stars might look during different stages of their evolution.

Provided by Harvard-Smithsonian Center for Astrophysics 

NASA Provides New Funding to Asteroid Search Program

The asteroid 2012 DA14 currently has the greatest chance of impacting Earth, possibly crashing down on Feb. 16, 2020. NASA

The search for potentially dangerous asteroids will continue through 2015 after federal funders agreed to give the NASA-funded Catalina Sky Survey, a $4.1 million funding boost, researchers announced.

The survey uses two telescopes run by the University of Arizona to scan the sky for objects that enter a collision course with Earth.

The new funds will be used to upgrade the program's telescopes, something researchers said is sorely needed.

"When we began observing in 2000, our image sensor was 16 megapixels, which was large by any standard," Steve Larson, a Catalina Sky Survey researcher and senior staff scientist at University of Arizona, said in a statement.

"Today, commonly available consumer digital cameras have surpassed that size, and we were reaching the limit of productivity with our current camera design."

The new telescopes will quadruple the amount of sky the telescopes cover each month.

The asteroid watchers also plan to use the new money to develop more sensitive software and conduct more searches.

The Catalina Sky Survey uses two telescopes to take images of a selected part of the sky roughly 10 minutes apart, according to a press release.

A computer program then scrutinizes the images to identify objects moving in a straight line.

If the object qualifies as a near-Earth object (NEO), an object whose trajectory will bring it close to Earth, the survey reports it to the Smithsonian Institution in Washington, D.C.

The survey discovered 586 near-Earth asteroids in 2011, 65 percent of all NEOs discovered.

"NASA has recognized that over the last seven years, our program has constantly strived to improve its performance, and has collaborated with others to find new ways to exploit the nearly 1,000 images we take every night with our two telescopes in the mountains north of Tucson," Edward Beshore, principal investigator of the Catalina Sky Survey, said in a statement. "I think NASA recognizes the CSS as a valuable service to, well, humanity."

Congress mandated the Spaceguard Survey, which the Catalina Sky Survey is a part of, in 1998.

The Spaceguard Survey required 90 percent of NEO's over 1 km in diameter to be found by 2008.

As of 2011, researchers found 911 NEO's through the Spaceguard program and expect 70 more objects will be found, according to NASA.

NASA tracks every NEO that has a chance of colliding with Earth in the next 100 years.

Asteroid 2011 AG5: A Reality Check

Asteroid 2011 AG5 has been receiving a lot of attention lately because of a very unlikely scenario which would place it on an Earth-interception course 28 years from now.

Here is a scientific reality check of this relatively nondescript space rock which is currently ranked a "1" on the 1 to 10 Torino Impact Hazard Scale

As of Feb. 26, 2012, asteroid 2011 AG5 is one of 8,744 near-Earth objects that have been discovered.

It is approximately 460 feet (140 meters) in size and its orbit carries it as far out as beyond Mars' orbit and as close to the sun as halfway between Earth and Venus.

It was discovered on Jan. 8, 2011, by astronomers using a 60-inch Cassegrain reflector telescope located at the summit of Mount Lemmon in the Catalina Mountains north of Tucson, Arizona.

Due to its current location in the daytime sky, observations of 2011 AG5 cannot be made by Earth-based telescopes, so its orbit has not yet been determined to a level where scientists can confidently project its location decades into the future. But that day is coming.

"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.

NASA: Portrait of a Doomed Asteroid

A new study provides a possible explanation of mysterious X-ray flares detected by the Chandra K-ray Observatory for several years in the region of Sagittarius A*, or Sgr A*.

The study suggests a cloud around Sgr A*, a supermassive black hole at the center of our Milky Way Galaxy, which contains hundreds of trillions of asteroids and comets that have been stripped from their parent stars.

The flares occur when asteroids of six miles or larger in radius are consumed by the black hole.

An asteroid that undergoes a close encounter with another object, such as a star or planet, can be thrown into an orbit headed towards Sgr A*.

If the asteroid passes within about 100 million miles of the black hole, roughly the distance between the Earth and the sun, it is torn into pieces by the tidal forces from the black hole.

These fragments would then be vapourised by friction as they pass through the hot, thin gas flowing onto Sgr A*, similar to a meteor heating up and glowing as it falls through Earth's atmosphere.

A flare is produced and eventually the remains of the asteroid are swallowed by the black hole.

Image Credit: Illustrations: NASA/CXC/M.Weiss

Near Earth Asteroid's near-miss

An Asteroid, estimated to be about 36ft in diameter, will pass within around 37,000 miles of the Earth at 4pm.

Although the asteroid – named 2012 BX34 – will travel past less than a fifth of the distance to the Moon, experts said there is no cause for concern.

"It's one of the closest approaches recorded," said Gareth Williams, associate director of the US-based Minor Planet Center.

"It makes it in to the top 20 closest approaches, but it's sufficiently far away ... that there's absolutely no chance of it hitting us," he told the BBC.

The asteroid's path makes it the closest space-rock to pass by the Earth since object 2011 MD in June 2011.

arlier estimates put the asteroid's closest distance at as little as 12,000 miles, near the distance at which geostationary satellites reside, but observations overnight showed it will pass at a more comfortable distance.

Although the asteroid will not be visible to the naked eye, Dr Williams said that keen backyard astronomers could get a look.

MARS HiRISE Image: Very Fresh Impact Crater Superposing a Wrinkle Ridge in Hesperia Planum

The ridge captured in this HiRISE image is called a wrinkle ridge.

This wrinkle ridge is located in Hesperia Planum, a region of over two million square kilometers (over 770,000 square miles) in the southern highlands of Mars.

It is located northwest of the Hellas basin and adjacent to Tyrrhena Patera and contains abundant orthogonal and intersecting wrinkle ridges.

Wrinkle ridges are long, winding topographic highs and are often characterized by a broad arch with superposed narrow asymmetric ridges. These features have also been identified on the Moon, Mercury, and Venus.

Their origin is attributed to horizontal compression or shortening of the crust due to faulting and folding. They commonly have asymmetrical cross sectional profiles and an offset in elevation on either side of the ridge.

Superposing or located on top of the wrinkle ridge, is a very fresh impact crater. We can tell that this crater is fresh because of its relatively sharp or crisp rim and unmodified shape.

If you look closely, you can see faint rays of relatively fine material, boulders, and smaller secondary craters radiating from the crater and superposing the wrinkle ridge and older surrounding craters.

Messenger Mercury: Collision With Giant Asteroid May Have Caused Spin Change

Updated NASA Messenger probe images obtained on September 29, 2011, shows a large crater with a floor partially covered by large numbers of Coalesced Hollows.

Mercury may have a lot in common with Earth, but close-up images and data captured by NASA'S MESSENGER probe this year show it's still a bit of a planetary weirdo. REUTERS/NASA/Handout

A new study suggests that Mercury's strange spin may have been caused by collision with a giant asteroid, which may have also caused Caloris Basin, Mercury's largest impact crater.

"Mercury once had a spin rate synchronous with the sun, like the moon with the Earth," said study co-author Alexandre Correia, a planetary scientist at the University of Aveiro in Portugal.

However, a giant asteroid may have collided with planet causing it to rotate three times on its axis for every two orbits it completes around the sun.

According to the study, computer models suggest that a giant impact from an asteroid knocked the planet it into its current strange configuration.

The space rock would have been at least 43 miles wide and 550 trillion metric tons in mass, or 1/600,000 the mass of Mercury, Correia said.

Evidence of the collision could include Mercury's largest impact crater, the Caloris Basin as it matches the predicted size, age and location of the impact.

Such an impact might also explain certain hollows seen on Mercury's surface, the researchers said.

Scientists had long assumed that Mercury was tidally locked with the sun, however, radar observations revealed that the planet led a far stranger life, rotating three times on its axis for every two orbits it completes around the sun.

Russian astronomers predict asteroid Apophis collision with Earth

Russian astronomers have predicted that asteroid Apophis may strike Earth on April 13, 2036.

"Apophis will approach Earth at a distance of 37,000-38,000 kilometers on April 13, 2029. Its likely collision with Earth may occur on April 13, 2036," Professor Leonid Sokolov of the St. Petersburg State University said.

The scientist said, however, the chance of a collision in 2036 was extremely slim saying that the asteroid would likely disintegrate into smaller parts and smaller collisions with Earth could occur in the following years.

"Our task is to consider various alternatives and develop scenarios and plans of action depending on the results of further observations of Apophis," Sokolov said.

The asteroid, discovered in 2004, is considered the largest threat to our planet, although NASA scientists reduced the likelihood of a hazardous strike with Earth in 2036.

Russia's space agency announced its plans earlier to consider a project to prevent the large asteroid from colliding with Earth.

Russia And Europe: Join Forces To Protect Earth From Asteroids

Russia And Europe May Join Forces To Protect Earth From Asteroids

Russian space officials and members of the European Commission will meet in early July to discuss joining forces against thousands of potentially hazardous asteroids, the head of the Russian Federal Space Agency Roscosmos said.

Despite the growing concern about the asteroid threat, no anti-asteroid defense programs have been developed in practice so far, with only several theoretical concepts being studied. At a meeting in Moscow on July 7, the European Commission will consider Roscosmos's proposal to start a joint anti-asteroid project with the European Union.

"I received a letter, in which the European Commission proposes to meet on July 7 in Roscosmos with scientists and engineers of the Federal Space Agency, the Russian Academy of Sciences and other institutions and organizations. At the meeting, the Russian bid to start a joint project with the EU will be considered," Anatoly Perminov said.

In his Wednesday's report to Roscosmos, the head of the Astronomy Institute at the Russian Academy of Sciences, Boris Shustov, said Russian scientists had detected a total of 6,960 near-Earth asteroids (NEAs) as of April 10.

The vast majority - 6,070 space bodies, or 87.2% of the total - are asteroids measuring from 100 meters to 1,000 meters in diameter. Others are 48 comets (1.2%) and 806 asteroids measuring more than a thousand of meters in diameter (11.6 %).

Short Sharp Science: Asteroid strike may have frozen Antarctica

Short Sharp Science: Asteroid strike may have frozen Antarctica

A massive asteroid hit the Timor Sea around 35 million years ago - and the impact apparently contributed to the formation of the Antarctic ice sheets.

So says Andrew Glikson, a specialist in the study of extraterrestrial impacts, from the Planetary Science Institute at the Australian National University in Canberra, who analysed a dome found 2.5 kilometres below the Timor Sea, about 300 kilometres off Australia's north west coast.

Based on the structure of the dome, called Mount Ashmore, there were two obvious explanations for its formation: from a mud volcano or from the movement of tectonic plates.

But using a barrage of tests including scanning electron microscopy and seismic surveys, as well as chemical analysis of the rocks, Glikson concluded that the dome was the result of an asteroid crashing into the Earth at such speeds that it caused the Earth's crust to rebound (Australian Journal of Earth Sciences, DOI: 10.1080/08120099.2010.481327).

Images from scanning electron microscopy showed that the cracks and pulverised rocks throughout the dome were unlike those seen in tectonic plate movements.