Categories: Asteroids

Science Team Determines Composition of Asteroid Itokawa

Asteroid Itokawa. Image credit: JAXA. Click to enlarge
Itokawa, a spud-shaped, near-Earth asteroid, consists mainly of the minerals olivine and pyroxene, a mineral composition similar to a class of stony meteorites that have pelted Earth in the past.

This asteroid ingredient list, published in Science, comes courtesy of Hayabusa, the spacecraft launched in 2003 by the Japanese Aerospace Exploration Agency (JAXA). The mission of Hayabusa is to bring back first-ever samples from an asteroid to better understand their role as building blocks of the solar system.

Itokawa, an elongated rocky object nearly as long as five football fields, circles the sun more than 321 million miles away from Earth. Along with a few hundred known asteroids, Itokawa’s orbit is close to Earth’s orbit and was discovered by the Lincoln Near-Earth Asteroid (LINEAR) program, which detects near-Earth asteroids and provides advance warning if any are bound for Earth. Itokawa doesn’t currently pose such a threat, but its close proximity made it a tempting scientific target.

A near-infrared spectrometer aboard Hayabusa helped identify Itokawa’s mineralogy, mostly a mixture of the rock-forming minerals olivine and pryroxene, and possibly some plagioclase and metallic iron. But to truly understand what they had, the team turned to Takahiro Hiroi, a Brown University researcher who is expert in determining the composition of asteroids and meteorites, bits of asteroids that have fallen to Earth.

Hiroi is a senior research associate in the Department of Geological Sciences at Brown and the operations manager of the University’s NASA-funded Reflectance Experiment Laboratory (RELAB). For the Hayabusa project, Hiroi obtained samples of meteorites from museums, measured them at RELAB, and compared these results with spectral data from Itokawa.

Hiroi was able to determine that the mineral composition of the surface of Itokawa was similar to that of LL chondrites, a common class of stony meteorites relatively low in metallic iron. This link helped the team place a probable source of origin for Itokawa: the inner portion of the main asteroid belt, a ring of tens of thousands of rocks orbiting the sun between Mars and Jupiter.

Using Hayabusa data, the team was also able to better describe the surface of Itokawa. Much of it is studded with boulders, although the asteroid contains a smoother area known as Muses Sea. This diversity of terrain, the team concludes, may be the result of past meteoroid impacts and space weathering, a rock-altering process due to bombardments by dust particles and solar wind.

“We’ve never had a close-up look at such a small asteroid until now,” Hiroi said. “Large asteroids such as Eros are completely covered with a thick regolith, a blanket of looser material created by space weathering. With Itokawa, we believe we have witnessed a developing stage of the formation of this regolith. And these boulders sitting on Itokawa are no different from the meteorites that have fallen on Earth. So we may be seeing an earlier stage of asteroid evolution, of a type that has touched this planet.”

NASA and JAXA funded the work.

Original Source: Brown University

Fraser Cain

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay. Here's a link to my Mastodon account.

Recent Posts

Webb Confirms a Longstanding Galaxy Model

The spectra of distant galaxies shows that dying sun-like stars, not supernovae, enrich galaxies the…

4 hours ago

The Aftermath of a Neutron Star Collision Resembles the Conditions in the Early Universe

Neutron stars are extraordinarily dense objects, the densest in the Universe. They pack a lot…

4 hours ago

New View of Venus Reveals Previously Hidden Impact Craters

Think of the Moon and most people will imagine a barren world pockmarked with craters.…

7 hours ago

Multimode Propulsion Could Revolutionize How We Launch Things to Space

In a few years, as part of the Artemis Program, NASA will send the "first…

18 hours ago

China Trains Next Batch of Taikonauts

China has a fabulously rich history when it comes to space travel and was among…

19 hours ago

NASA Focusses in on Artemis III Landing Sites.

It was 1969 that humans first set foot on the Moon. Back then, the Apollo…

20 hours ago