What Genesis Solar Particles Can Tell Us

The recent crash of NASA’s Genesis space probe may have looked like bad
news for scientists, but its cargo of particles captured from the sun
should still yield useful information, according to Qing-Zhu Yin, a
planetary scientist at UC Davis.

Yin, who is not directly affiliated with the Genesis mission, studies
the composition of meteorites to learn about the formation of the solar
system. Like the Genesis capsule, meteorites have a hard landing on the
Earth, but can still yield useful information, he said.

By looking at the ratio of oxygen-16, -17 and -18 isotopes in the solar
particles, scientists should be able to test theories about how the sun
and planets formed. Oxygen-16 is by far the most common. The Earth,
moon, Mars and some meteorites all have slightly different ratios of the
three isotopes.

The oxygen makeup of the sun, which contains about 99.9 percent of all
the mass in the solar system, is much harder to measure. The Genesis
spacecraft was built to answer that question by collecting particles
blown out from the sun.

In a “Perspectives” article in the Sept. 17 issue of the journal
Science, Yin describes new theories about local variations in oxygen
isotopes in the vast dust and gas cloud around the young sun. Free
oxygen was released when ultraviolet light hit carbon monoxide gas.
Because oxygen-16 was so abundant, it was released mostly near the
surface of the cloud, but breakdown of carbon monoxide containing less
abundant oxygen-17 or -18 continued deeper into the cloud.

Free oxygen and hydrogen formed water that froze onto dust grains and
eventually formed into planets, preserving the oxygen-17 and -18
signature, Yin said. The models predict that the Sun itself should have
a much lower ratio of oxygen-17 and -18 to oxygen-16 than the rocky
planets, a prediction that can be tested by Genesis and future missions.