Fire and Ice

Seven years in space are a very long time, if you’re a scientist in Houston, but not very much at all if you’re a comet.  The two are colliding this afternoon, where NASA is talking about what the Stardust probe found from its rendezvous with a comet in 2004.

You’ll recall that Stardust, which passed less than 200 miles from comet Wild-2, gathered thousands of the grains that were streaming from it, sealed them in a return capsule, and landed them in the Utah desert in January.  Scientists in a Houston lab have been looking at them.

The headline: "Remarkably, enough, we have found both fire and ice," says Donald Brownlee, the Principal Investigator for the project.

Here’s what he’s saying:

Wild-2, like most other comets, has spent most of its existence in the far reaches of the Solar System, in the cold reaches where the temperature is close to absolute zero. 

Nevertheless, many the grains collected by the Stardust probe are made of compounds that could only formed under extremely high temperatures.  Stuff like olivine and titanium nitrite–not household names, but they’re fairly common around the planets close to the Sun.

How could this be?  Brownlee offers two theories:

1) The particles formed near the Sun as it was forming, when the Solar System was still a giant disk of dust and debris…and somehow, they were flung outward toward the outer edge of that disk.  They’re something like 4.6 billion years old, and have spent most of their time out in the cold darkness of deep space.  How did they get out there?  The physicists are working on the possibilities.

2) The particles may actually have come from other stars.  They were flung out from those distant places (the nearest star is 4.3 light years away), and spent millions or billions of years flying through interstellar space. 

If that’s so, the scientists were vindicated in their decision to call their ship "Stardust."  It only traveled a few hundred million miles from Earth, but may have found real…star dust.

(Stardust home page: http://www.nasa.gov/mission_pages/stardust/main/index.html)