Tag Archives: Hayabusa

Sunlight rolled the rocks on an asteroid

Scientists studying the rounded rocks on the surface of the asteroid 25143 Itokawa, photographed by the Japanese probe Hayabusa, have concluded that sunlight combined with the asteroid’s tiny gravity caused them move and thus erode themselves.

As sunlight bounced off the orbiting boulders, photons provided a tiny push. As they radiated back outward as heat, they triggered a recoil effect that added a gentle spin. Over time, these slowly spinning boulders bumped into each other with enough force to wear their edges into smooth surfaces.

Warning! This is only a model, and thus could very well be wrong. It is reasonable however and worth considering as a factor in studying the early formation history of asteroids.

Avalanches on an asteroid

A new analysis predicts that when the asteroid Apophis flies past the Earth in 2029, the close fly-by will cause avalanches on the asteroid.

If asteroids pass close to Earth, they begin to experience the effects of our planet’s gravity. Just like the moon pushes and pulls the oceans, creating the tides, asteroids are susceptible to tidal forces from our planet. To judge what effect this will have on Apophis, scientists need to know what it’s made of. Their best guess is based on photos taken by a Japanese spacecraft named Hayabusa, which took detailed pictures of an Apophis-sized asteroid named Itokawa. Those images revealed that the asteroid wasn’t a solid mass of rock spinning through space, but rather a giant clump of debris held together loosely by gravity. “You look at the [Hayabusa] pictures and you’re like, ‘Uh, that’s a pile of rocks, dude.’ It’s very likely that Apophis is similar,” says astrophysicist Derek Richardson of the University of Maryland, College Park.

To show that Earth’s gravity could cause some of these rocks to tumble, Richardson and his colleagues developed a computer model that allowed them to place virtual sand piles across the surface of a model asteroid with roughly the same dimensions as Apophis. By factoring in the gravity from the asteroid, the tidal force from Earth, centrifugal force caused by the asteroid’s rotation, inertial forces, and other effects, the team was able to predict how the particles on the surface of the asteroid would behave on approach. The results confirm that Earth’s tidal forces would be strong enough to cause tiny avalanches on the asteroid, the team reported online ahead of print in Icarus.

Need I note that there are a lot of uncertainties here? Because they are using what is known about a different asteroid, all of their assumptions about Apophis’s properties in their computer model could be very wrong.

Still, this is interesting, because it does demonstrate that an asteroid could be significantly disturbed simply by flying past a planet.

First results from the Hayabusa asteroid samples

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.

Results from Hayabusa delayed till next year

We won’t know if the Japanese probe Hayabusa actually brought asteroid materials back to Earth until spring 2011. Key quote from the project scientist:

Kawaguchi said his science team found “tens of particles” in Chamber A of the canister. The tiny particles are being removed one-by-one in an extraction process that is stretching longer than anticipated.

Note that they still have not opened Chamber B, which is thought to have had a better chance of capturing asteroid material because it was the chamber in contact with the asteroid Itokawa.

First photos from inside Hayabusa capsule

Update and bumped: More details have been released about what was inside the Hayabusa capsule. In total, two 0.01 millimeter particles have been found in the inner capsule, and about 10 large particles in the outer capsule.

The first photo from inside the Hayabusa capsule has been released, showing the presence of a tiny 0.01 millimeter particle. It is still unknown whether this is an asteroid particle or something captured on the return to Earth.