3 Things We Learned From Japan’s Asteroid-Visiting Spacecraft, Hayabusa

Today, the Japan Aerospace Exploration Agency (JAXA) released its analyses of the first asteroid samples ever transported back to Earth. Looking deep into the chemistry of the loose surface material, or regolith, that JAXA?s Hayabusa spacecraft recovered has revealed clues about this particular asteroid, the origin of the meteorites that fall to Earth and perhaps even a little about the history of the solar system.

JAXA launched its autonomous lander, Hayabusa, in 2003 and aimed it toward asteroid 25143 Itokawa, 200 million miles away. The mission was riddled with malfunctions, but two years later, the little spacecraft that barely could snatched dust from the surface of the asteroid. Hayabusa?s return capsule made it back to Earth last summer carrying only 1 microgram (one-millionth of a gram) of sample rock. Since then, teams of scientists have been carefully analyzing it in Japanese labs.

?That whole mission was nail-biting,? says Michael Zolensky of Houston?s Johnson Space Center, one of just two NASA scientists who helped analyze the samples in Japan. The surviving sample size is so tiny, in fact, that JAXA is reserving more than half until technology advances to a point that they can analyze the dust even more carefully. (Ten percent of the microgram is being transported to Johnson in December.) Until then, this is what we know:

1. Most Meteorites on Earth Originated From Asteroids Like Itokawa.

Itokawa is a small, near-Earth asteroid with a stony, or S-type, surface. S-type asteroids are the most common type found in the inner and middle parts of the Asteroid Belt between Mars and Jupiter. Scientists had long believed that they were the parent bodies of chondrites, the most common type of meteorites that land on Earth. But based on previous methods of comparisons, such as remote observations, they could not be sure.

?There weren?t any good spectra matches and no one really knew why,? Zolensky says. Because astronomers lacked actual asteroid samples, they couldn?t gauge how space weathering and solar wind (ejections from the sun) were affecting the asteroids? properties. Instead, scientists had been using surface samples from the moon collected by American and Soviet astronauts in the 1960s and ?70s to approximate asteroid weathering.

The new tests revealed that the S-type particles are identical to ordinary chondrites. Space weather and solar winds had chemically altered the lunar regolith much more than it affected the asteroid regolith, which is why scientists had been thrown off.

?These samples are the Rosetta Stone for meteorite IDing,? Zolensky says. ?Now we can relate tens of thousands of meteorites on the ground to their parent asteroids in the sky.?

2. This Asteroid Was Shattered.

Itokawa is peanut-shaped; its gravity is strong enough to keep itself together, but too weak to pull itself into a sphere. By analyzing the size and chemistry of the dust samples, scientists found that the asteroid experienced major temperature and impact shocks and probably used to be 40 times bigger.

?This asteroid was ripped apart at some point,? Zolensky says. Most likely, another asteroid rammed and shattered it. ?Most of it was lost, but some of the fragments reformed into what it is today.?

Knowing how the asteroid is held together and what it?s made of could prove to be extremely important information if, say, a similar asteroid ever threatened to hit the Earth. Zolensky says that if scientists know the rock?s properties, tailor-made missiles could be launched to blow it up.

3. The Samples Are So Old, They Could Hold the History of the Solar System.

Chondrites are from the most primitive rocks in the universe. Because these asteroids are so small, scientists believe they experience much less in the way of interior thermal processes than planets do. As a result, chondrites today are much closer to their original state, which provides a window to the early days of the solar system.

By combining this data with data from other collection missions (NASA?s Stardust brought back comet samples; Genesis brought back solar wind), scientists can learn about the solar system?s evolution. Unfortunately, none of these missions have returned any water-bearing minerals, which are essential to understand where Earth?s organics came from. ?We have to increase the diversity of asteroids that we?re sampling,? Zolensky says.

National space agencies are trying to do just that. In 2014 JAXA will launch Hayabusa-2 to a different type of asteroid, and in 2016 NASA will launch OSIRUS-Rex to a third type of asteroid. One, hopefully, will return with asteroid gold: H₂O.

Source: http://www.popularmechanics.com/science/space/deep/3-things-we-learned-from-japans-asteroid-visiting-spacecraft-hayabusa?src=rss

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