By Ron Cowen
BALTIMORE — Examining a dusty disk — a sign of planet formation — around a young star, astronomers appear to have found a new clue about how the youthful Earth acquired water to form oceans and provide a habitat for life.
The disk of debris surrounds the 10-million-year-old star EF Chamaeleontis, which lies about 310 light-years from Earth. Previous observations with NASA’s infrared Spitzer Space Telescope showed that the dust is relatively warm. That suggests the radiation is most likely generated by collisions between bits of material, or planetesimals, in the region around the stars where rocky, terrestrial planets could form.
In the new study, Thayne Currie of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleagues used a spectrometer on Spitzer to separate the infrared emissions into individual wavelengths that would enable the scientists to identify the composition of material within the warm disk. Currie and his collaborators found that the emissions resemble those from a mixture of several minerals known as phyllosilicates, which can form only in the presence of liquid water. In the solar system, planetesimals laden with phyllosilicates are thought to have rained down on Earth from the asteroid belt or the more distant Kuiper belt of comets, delivering the water that became the planet’s oceans.
The presence of phyllosilicates in the terrestrial planet-forming zone of disks surrounding young stars may therefore trace water delivery to fledgling terrestrial planets, Currie notes. “To our knowledge, this is the first bona fide detection of phyllosilicates in a debris disk,” he says.