Chinese flyby of asteroid shows space rock is "rubble"

Dec 12, 2013
"Outbound images of Toutatis acquired on 13 December, 2012 during Chang'e-2 flyby, indicative of the spacecraft being away from the asteroid (from a to e). The imaging distance (D), epoch of flyby (T, UTC) and resolution of each image (R) are shown for each snapshot. The nearest distance between the probe and the surface of the asteroid is about 770m." Credit: CNSA (China National Space Administration).

China's first flyby of an asteroid shows that a gigantic space rock which once triggered a doomsday scare is essentially rubble, scientists reported on Thursday.

On December 13 2012, a lunar probe called Chang'e-2 rendezvoused with asteroid 4179 Toutatis as the rock, bigger than a city block, swept by Earth at a distance of around seven million kilometres (4.4 million miles).

Describing the encounter in detail in the journal Scientific Reports, Chinese scientists said the flyby was brief but highly successful, the result of seven months of preparation after Chang'e-2 had completed its primary mission of orbiting the Moon.

Advancing at more than 38,000 kilometres (24,000) miles per hour, the probe came within 770 metres (yards) of the asteroid's surface, returning pictures with a resolution better than three metres (10 feet) per pixel.

The images show a rock shaped like a piece of ginger root, 4.75 kilometres (2.96 miles) long by 1.95 kms (1.21 miles) wide, with a crater at its big end showing an impact at some point in its history.

The astronomers also saw boulders and small gravel-like stones called regolith sliding over its surface, which suggest that Toutatis is not so much a single, solid rock but more an assembly of rubble.

"The rubble-pile structure is essentially a normal situation for most of the smaller asteroids" under a kilometre (0.6 of a mile) across, said Ji Jianghui of the Chinese Academy of Sciences in Beijing.

"This is also the case for Toutatis. In this structure, the asteroids are not a single rock but a loose collection of fragments under the influence of gravity, which means that it is an agglomeration of gravitationally-bound chunks," Ji said in an email exchange with AFP.

Toutatis was first spotted in 1934 and then lost from sight. It was then rediscovered in 1989 by a French astronomer, Christian Pollas, who named it after a Celtic god, Toutatis, which also features as a name of doom in the "Asterix" comic books.

Internet panic in 2004 flyby

Toutatis is one of the biggest "potentially hazardous asteroids," or PHAs, or rogue rocks whose orbit can bring them close to our planet.

As a result, it has been closely followed by telescopes and radar on Earth.

It came by Earth in 1992, 1996, 2000, 2004, 2008 and 2012, but will not approach so close until 2069.

In the runup to the 2004 flypast, panicky rumours spread on the Internet that NASA had either lied or got its calculations wrong, and that Earth was going to take a direct hit.

As predicted, Toutatis whizzed past safely at 0.1 Astronomical Units, or 1.5 million kilometres (930,000 miles), equivalent to about four times the distance between the Earth and the Moon. In 2069, the gap is expected to be twice that, at 0.2 Astronomical Units.

Ji said that, even though Toutatis seems to have a loose structure, it was unlikely to fall apart, even when tugged by the gravity of nearby planets.

"It seems that Toutatis will not break apart into two separate parts due to its current slow rotational status when it comes to Earth or other planets," he said.

Toutatis is not a known threat, but there are plenty of other asteroids whose orbital track is unknown but which may bring them across our path.

Understanding the structure of these rocks is essential for deciding how best to defend Earth against an impact, said Ji.

"The impact threat from near-Earth objects always exists," he said.

"Currently, Toutatis will not collide Earth, whereas (there are) millions of smaller-sized objects, on the scale of several tens of metres (yards) across," he said.

"Depending on the physical features and internal structures for PHAs, different solutions are applicable to them... the mitigation may be carried out such as by blowing the entire asteroid up or pulling them away from their dangerous orbits to deflect them."

Chang'e-2 is now more than 50 million kilometres (30 million miles) from Earth, helping to test control procedures and orientation in space flight.

China is the fourth space power to have directly explored an asteroid, after the United States, Europe and Japan.

Explore further: PanSTARRS K1, the comet that keeps going

More information:

add to favorites email to friend print save as pdf

Related Stories

Asteroid Toutatis tumbles by Earth

Dec 13, 2012

While Asteroid 4179 Toutatis was never a threat to hit Earth during its quite-distant pass on Dec. 11-12, astronomers were keeping their instruments and eyes on this space rock to learn more about it, as ...

Asteroid Toutatis slowly tumbles by earth

Dec 17, 2012

(—Scientists working with NASA's 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif., have generated a series of radar data images of a three-mile-long (4.8-kilometer) asteroid ...

Big asteroid swinging by Earth has its own moon

May 30, 2013

Astronomers getting their first close-up glimpse of a giant asteroid about to whiz by Earth found a surprise bonus rock. A smaller moon asteroid is circling the larger space rock, an unusual but not unheard ...

NASA radar images asteroid 2007 PA8

Nov 06, 2012

(—Scientists working with NASA's 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif., have obtained several radar images depicting near-Earth asteroid 2007 PA8. The images ...

Nine radar images of asteroid 2007 PA8

Nov 27, 2012

(—A collage shows nine radar images of near-Earth asteroid 2007 PA8 that were obtained between Oct. 31 and Nov. 13, 2012, with data collected by NASA's 230-foot-wide (70-meter) Deep Space Network ...

Recommended for you

Student to live in simulated space habitat

1 hour ago

A Purdue University industrial engineering doctoral student is among six "crew members" spending the next eight months in a domed habitat on a volcanic landscape mimicking life on a Martian outpost.

The wake-up call that sent hearts racing

4 hours ago

"But as the minutes ticked by, the relaxed attitude of many of us began to dissolve into apprehension. Our levels of adrenaline and worry began to rise."

US-India to collaborate on Mars exploration

13 hours ago

The United States and India, fresh from sending their own respective spacecraft into Mars' orbit earlier this month, on Tuesday agreed to cooperate on future exploration of the Red Planet.

Swift mission observes mega flares from a mini star

13 hours ago

On April 23, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf star. The initial blast from this record-setting series ...

Sandblasting winds shift Mars' landscape

18 hours ago

High winds are a near-daily force on the surface of Mars, carving out a landscape of shifting dunes and posing a challenge to exploration, scientists said Tuesday.

PanSTARRS K1, the comet that keeps going

21 hours ago

Thank you K1 PanSTARRS for hanging in there! Some comets crumble and fade away. Others linger a few months and move on. But after looping across the night sky for more than a year, this one is nowhere near ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Dec 12, 2013
the Chinese space program really made great use of the investment.
1 / 5 (1) Dec 13, 2013
The issue of an impact, though real, is a distraction from the real mission- which I believe is to source raw materials from outside a gravity well.
Whoever colonises the la Grange points will be the gatekeepers to the cosmos. The cosmos will be by invitation only.
It looks as though the gatekeepers are not going to be the world's parasites. So this is going to turn out well.
5 / 5 (2) Dec 13, 2013
Whoever colonises the la Grange points will be the gatekeepers to the cosmos

That is silly. You're far better off establishing outposts at locations that have some advantage of resources, especially water. If it turns out that the moon does have water in a useful form at its poles, then the permanently sunlit rims of permanently shaded craters with water ice in them will be the beach-front property of the solar system. You can do some really cool things with heat exchangers when you have +200 and -200 celcius within a few meters of eachother, and a cache of water, not matter how small, is a big bonus too.

It looks as though the gatekeepers are not going to be the world's parasites

Whatever country you live in, if you are ever caught in a major natural disaster, and the US Navy shows up to help (like we always do) I certainly hope you tell them "no thanks" and that you're waiting for China to come help you. Good luck.