TNOs: could some have formed elsewhere? Options

[elakdawalla]

I got a question today for Planetary Radio Q&A that I couldn't answer, being pretty ignorant about solar system formation research. Can anybody help?

We know from the metal composition of our solar system that the Sun is at least a second or third generation star. It made me wonder if it was possible that some of the comets or other KBOs that we witness might be from the Sun's predecessor star or stars. If not, could such bodies exist a bit further out? I should think it would be fantastic to be able to investigate such objects.

--Emily

[dvandorn]

Not looking for the unexpected is a slippery slope. If you have the time and luxury to develop and use a multi-approach instrument suite, designed to gather as much possible information about as many characteristics of a phenomenon as possible, then it is, indeed, a cardinal sin to ignore all results except the ones that you wanted to see.

But planetary probes, in specific, are so mass-limited that you have to design your instruments carefully. You inevitably design your instruments to constrain existing theories, or to look for a very small subset of the available information that directly relates to what's seen as a pivotal prediction of a given theory.

We have two fabulous little robotic geological explorers on Mars right now, and yet they are incapable of analyzing the oxidation properties of the soils. They couldn't find organics if they were strewn over the surface liberally. They are designed almost solely to identify hydration effects on the rocks and to identify a *limited* range of minerals in the rocks and soils. Because they were designed to constrain current theories on the effects of water on the Martian surface.

So, with the MERs, we're not ignoring unexpected information -- we designed them to return *only* information about expected conditions. At least on several levels. (I admit freely that the Pancam returns a wide variety of data, and we see in its images not only what we expected but much that we didn't. I'm really speaking only of the non-imaging experiments, here. But that really does show you the value of imagery...)

This is not a condemnation of the process. Planetary probes are so mass-limited that you *must* tailor their instrumentation suites to gather that subset of the available information you think is going to be the most valuable and worthwhile. You just can't afford to put every sensor you can think of on such probes.

The trap here is in the phrase "information you think is going to be the most valuable." The only path to that kind of judgment is illuminated by best theories. So, we get trapped into designing our probes to constrain, prove or disprove best current theory. Which works against looking for the unexpected.

-the other Doug