Orion: a possible interstellar dust particle

We are reporting today on by far the most promising interstellar dust candidate found to date. We emphasize that we do not yet know whether or not it is actually interstellar — this may take years to determine definitively. Nevertheless, we are cautiously optimistic that it is in fact a tiny piece of matter from outside our solar system.

Here is the story of this track.

Track 30 is one of a small population of so-called “midnight” tracks — that is, tracks entered the collector at an angle and that are pointing more or less straight up towards 12 o’clock on the clock face. You will notice that this is an “off-normal” track like those seen in the training movies, but does not resemble the calibration tracks that we used in Stardust@home phase 1 and 2 for scoring. It is clear that we would not have found this track without the intelligent and observant Stardust@home dusters — if we had used a computer algorithm, we probably would have missed it entirely.

The candidate was first identified by Bruce Hudson, and promoted to the Red Team alpha page by Red Team member Fred Grey. Bruce has named the particle “Orion”. You can see the candidate on the lower left corner of this focus movie.

The track was extracted from tile 43 by Dave Frank at NASA/JSC in Houston, and mounted on a micropicklefork. Dave sent it to Berkeley, where we remounted it between silicon nitride windows to prepare for analyses.

The particle has been through three analyses so far.

First, it was analyzed for the presence of organic material using Fourier Transform Infrared Spectroscopy (FTIR) by George Flynn at the National Synchrotron Light Source at Brookhaven National Laboratory on Long Island. George is a professor at SUNY Plattsburgh. FTIR is an extremely gentle technique and is something that we have done with all of our candidates so far. No evidence for any organic material was found in this track (or, for that matter, in any of the other candidates that we’ve analyzed in this way.)

Second, it went to Frank Brenker and his colleagues. Frank is a professor at the University of Frankfurt. They analyzed this particle on beamline ID13 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. They used x-ray fluorescence microscopy and x-ray diffraction. What they found was that the particle appears to be quite complex and fine-grained, and also has a composition for most elements similar to the so-called “cosmic” abundances. All of this points to an extraterrestrial origin.

Finally, it came back to Berkeley. Last week we (Anna Butterworth, Tolek Tyliszczak, Zack Gainsforth and I) analyzed it here on beamline 11.0.2 at the Advanced Light Source at LBL. We confirmed the results from ESRF but also were able to analyze lighter elements that cannot be detected on ID13 — magnesium and aluminum in particular. The particle is indeed quite complex, and again appears to be consistent with an extraterrestrial origin, although we are still analyzing our data, so this is quite preliminary.

So, we are quite excited. We may (emphasis on the word “may”) have the first sample of solid material from outside the solar system. Or it may be a false alarm.

We are reporting the first of these results at the Lunar and Planetary Science Conference in March. The abstract is here. Notice that four co-authors on this paper are the Stardust@home dusters who discovered the four “midnight” particles that we discuss in the abstract.

Soon I will post a narrated “ISPE update” slideshow describing these results in more detail. We are also busy preparing for Stardust@home phase 3, which will be focused on identifying more of these “midnight” tracks. We desperately need more of them!