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Monday, August 15, 2011

Anomalies in planet composition


Conventional wisdom holds that planetary systems form as clouds of dust and gas coalesce into a central star and orbiting planets.  If true, then the star and all the planets, moons, asteroids, etc that originated from that cloud should be composed of the same atomic elements.  According to a couple of new papers, this is not the case.

Both studies outlined differences in isotope ratios found in the solar wind (particles ejected from the sun’s atmosphere) from those found on Earth.  Many elements come in different flavors, or isotopes, depending on how many neutrons they have.  For example, oxygen always has eight protons, but may have eight (O16), nine (O17) or ten (O18) neutrons.  In the same way, nitrogen has seven protons, but seven (N14) or eight (N15) neutrons. Some isotopes are common and others are exceedingly rare.  However, the researchers expected to find that the ratios of isotopes coming from the sun would be the same as the ratios found on Earth.  Not so.

The first paper, by Kevin McKeegan of UCLA and his colleagues, outlined differences in oxygen isotope ratios found in the solar wind compared to those found here on Earth.  In the second paper, Bernard Marty of Nancy Universit√© and his colleagues looked at nitrogen isotope ratios with the same result.  In other words, the present isotopic makeup of the Earth does not match the solar material from which it was presumed to have co-formed.

Obviously, more work must be done to understand this.