Meteorite Monday: The Hayabusa mission to Itokawa

Last week I wrote briefly about the Japanese Hayabusa mission to the asteroid Itokawa. This mission was pretty cool because we went to this piece of space rock instead of waiting a piece of it to come to us. In spite of the mechanical failures that nearly scuttled the mission, the Hayabusa probe was able to collect dust from Itokawa and bring it home for us to study.

I wanted to write a bit about this mission because meteorites come from asteroids. This is the equivalent of studying not only pumice from Mt. Hood, but the origin of the volcano as a whole and its relation to the Cascades. The collected dust particles tell us the story of how Itokawa formed and the types of meteorites that could come from it. From this evidence we can also gain more insight into the formation of the solar system.

The dust particles tell us that Itokawa is not a single chunk of space rock. It’s actually a patchwork collection of various asteroids that were broken apart and coalesced into a single piece of rock (1). In geology parlance we call this a breccia– or a big pile of rubble that cemented together over time. Sometimes this breccia is made up of the same rock type, other times it’s not.

This mega breccia of Titus Canyon can be seen as a terrestrial analog to the composition of Itokawa (Image from the National Scenic Byways Program)

In the case of Itokawa, we learned that it’s composed of asteroids with different thermal characteristics. Some of the breccia pieces have seen little heating and contain glass and clinopyroxene- a mineral common to type 3 and 4 meteorites. Others contain minerals such as diopside and large plagioclase crystals- these are indicators of the type 5 and 6 meteorites that have seen a higher degree of heating. (Nakamura et al., 2011)

From this information Nakamura et al.,  were able to construct a history for Itokawa. They suggest that Itokawa was large enough to undergo a high degree of thermal metamorphism, but was subsequently broken apart by collisions with other asteroids. These pieces fused together into the much smaller Itokawa that is present today. They also confirm that Itokawa is a member of the S-type asteroid family and that a direct link exists between it and ordinary chondrites.

A close-up of the surface of Itokawa. (Image courtesy of JAXA)

Muses Sea is the region from which Hayabusa took its samples. (Image from JAXA)

1. Nakamura, Tomoki, et al., Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites. Science 333, 1113 (2011). DOI: 10.1126/science.1207758

2. For more close-ups of Itokawa, check out the image archive from JAXA.

Meteorite Monday: Asteroid Itokawa and the Hayabusa probe

Last week Science magazine published six articles about the results of the Japanese Aerospace Exploration Agency’s (JAXA) mission to asteroid Itokawa. In 2003 they sent a probe, Hayabusa, to gather information about Itokawa and collect soil samples.The poor space probe was plagued by malfunctioning engines, a rogue solar flare that fried computer systems and a mini-probe that failed to operate as it was designed. To JAXA’s credit, they still managed to collect dust from the surface of Itokawa and bring those particles back to earth for us to study.

Thanks to an acquaintance, Michael Barton, I was able to get my hands on one of the reports and I’ve been going through it with the hopes of sharing those results with my readers. Unfortunately, life has been rather hectic lately and I haven’t had the chance to properly read the paper and digest all the information in it.This may seem like a strange story for my Meteorite Monday column, but it makes sense when one considers that meteorites are just chunks of asteroids.

So, my goal for next week is to talk about some of the cool findings of this mission. Until then, you can click on the image to visit JAXA’s site and learn more about the Hayabusa and it’s mission to Itokawa.

Asteroid Itokawa (Image courtesy of JAXA)