|MadSci Network: Astronomy|
What an interesting question! My immediate answer would be "no, there isn't a unique fingerprint to our solar system" but that would be missing some of the detail because, in fact, there is a way to distinguish extrasolar material. The elements present in our solar system are the same elements that are present - as best we can tell - throughout the Universe. That is, astronomical observation has been able to detect all 92 naturally occuring elements in the emission lines from objects throughout the galaxy and beyond. And we have been able to observe the spectroscopic signatures of the same sorts of chemical compounds in the starlight of both distant stars and other galaxies as we find on Earth. In other words, it appears that both the building blocks of matter and the chemical compounds formed are invariant throughout all of visible space. Chemistry and the construction of compounds seems to be the same wherever we look. This is why I would say that we are not "special" or unique. There doesn't appear to be anything that is peculiar to our solar system and that would allow us to say that something was "extrasolar" versus "homegrown". Our solar system appears to be like any other in the galaxy. But having said this, not all meteorites are identical - meteorites being the pieces of asteroids or comets that would actually land here. While radiometric dating on these objects typically place their origins at around 4.5 billion years ago - which would be consistent with the age of the solar system and thus, appear to rule out extrasolar origins - there are other signs or indications that indeed some of the material that fills up space may be extrasolar (or maybe "pre-solar"). Any rock (or grain of dust) that passed between solar systems - between two neighbouring stars - would have to spend an enormously long period of time in the deep space. The length of time would ensure that the atoms present have been exposed to extreme levels of solar radiation. That is, they would have been exposed to the detrius in the solar wind for a long period of time. This might result in the capture protons or neutrons by some of the atoms, thereby resulting in unusual isotopic distributions relative to the rocks that we have found floating within our solar system. That is, they would have an isotopic signature that would be different from that typically found amongst material in the solar system. While we haven't found any "asteroids or comets" (or meteorites) with an isotopic pattern that would mark them as "extrasolar", the presolar grains of stardust that we have collected do show some remarkable variations in isotopic ratios. It would appear that a very small but definite percentage of the dust that permeates our solar system pre-dates the formation of the sun and planets and is "extrasolar" in origin insofar as the Sun is a second generation star formed from the left over dust and gas of previous stars. They would appear to be part of the interstellar medium from which our Solar System condensed long ago. However, having hung around the Solar System for the past 4.6 billion years, are they really "extrasolar"? As to how much is presently arriving from other stellar systems, there isn't a real good way to measure this. That is, how much of this stardust is of recent origin and not part of the cloud from which our solar system condensed is still a question mark. But it would seem likely that some of these grains must be from "out of town" and not just from our cosmic beginnings. The isotopic signatures found in dust grains does suggest that some of the stardust that permeates the solar system must not have originated here. So, does the local material have a unique fingerprint distinctive from the material around, say, Polaris? To the best of our knowledge, no, in the sense that the same isotopic distributions and the same sorts of chemical compounds present in our solar system have been observed around other systems. The elemental composition and the chemical compounds present here and there would appear to be the same. The compounds within different systems would appear to be the same. Is it then possible to see a fingerprint that would indicate that some of the material in the solar system is from "out of town"? Yes. Invariably the trip between systems will have resulted in transformations of the elements or the chemical compositions due the the prolonged journey between the stars. Such changes are detectable but will likely require that one look for material in outer space rather than on the surface of this planet. Space missions, like NASA's "Stardust", have collected data to be returned to Earth for analysis and will tell us a great deal about the composition of matter in outer space. Hopefully, some of the isotopic signatures will tell us more about pre-solar and extra-solar material - and might even allow us to distinguish between the two forms of stardust. Hope this answers your question.
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