Olivine makes Planets!

[Hunter Parasite]

NASA's Spitzer Space Telescope has spotted the very beginnings of what might become planets around the puniest of celestial orbs - brown dwarfs, or "failed stars."

Image right: This artist's concept shows microscopic crystals in the dusty disk surrounding a brown dwarf, or "failed star." The crystals, made up of a green mineral found on Earth called olivine, are thought to help seed the formation of planets.
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The telescope's infrared eyes have for the first time detected clumps of microscopic dust grains and tiny crystals orbiting five brown dwarfs. These clumps and crystals are thought to collide and further lump together to eventually make planets. Similar materials are seen in planet-forming regions around stars and in comets, the remnants of our own solar system's construction.

The findings provide evidence that brown dwarfs, despite being colder and dimmer than stars, undergo the same initial steps of the planet-building process.

"We are learning that the first stages of planet formation are more robust than previously believed," said Dr. Daniel Apai, an astronomer at the University of Arizona, Tucson, and member of the NASA Astrobiology Institute's Life and Planets Astrobiology Center. "Spitzer has given us the possibility to study how planets are built in widely different environments."

The observations also imply that brown dwarfs might be good targets for future planet-hunting missions. Astronomers do not know if life could exist on planets around brown dwarfs.

Brown dwarfs differ from stars largely due to their mass. They lack the mass to ignite internally and shine brightly. However, they are believed to arise like stars, out of thick clouds of gas and dust that collapse under their own weight. And like stars, brown dwarfs develop disks of gas and dust that circle around them. Spitzer has observed many of these disks, which glow at infrared wavelengths.

Apai and his team used Spitzer to collect detailed information on the minerals that make up the dust disks of six young brown dwarfs located 520 light-years away, in the Chamaeleon constellation. The six objects range in mass from about 40 to 70 times that of Jupiter, and they are roughly 1 to 3 million years old.

The astronomers discovered that five of the six disks contain dust particles that have crystallized and are sticking together in what may be the early phases of planet assembling. They found relatively large grains and many small crystals of a mineral called olivine.

"We are seeing processed particles that are linking up and growing in size," said Dr. Ilaria Pascucci, a co-author also of the University of Arizona. "This is exciting because we weren't sure if the disks of such cool objects would behave the same way that stellar disks do."

The team also noticed a flattening of the brown dwarfs' disks, which is another sign that dust is gathering up into planets.

A paper on these findings appears online today in Science. Authors of the paper also include Drs. Jeroen Bouwman, Thomas Henning and Cornelis P. Dullemond of the Max Planck Institute for Astronomy, Germany; and Dr. Antonella Natta of the Osservatorio Astrofisico di Arcetri, Italy.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spitzer's infrared spectrograph, which made the observations, was built by Cornell University, Ithaca, N.Y. Its development was led by Dr. Jim Houck of Cornell. The NASA Astrobiology Institute, founded in 1997, is a partnership between NASA, 16 major U.S. teams and six international consortia.

For artist concepts, graphics and more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer/ . For more information about the NASA Astrobiology Institute, visit http://nai.arc.nasa.gov/ . For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/ .


Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

2005-160

[maxim]

Olivine is a main crust mineral. But you surely can't say that it's the main element of a planet.

It's a silicate mineral that mainly contains mangan an iron. It /may/ help in formating planets, but so do hundreds of other elements too. It's green in it's pure form (and such used as kind of jewellry) but brown to black in it's natural form, so I doubt that dust disks would give a green impression. It's rather seldom on earth surface because it oxidates fast when getting in contact with oxygen.

maxim

[Malenfant]

Olivine is a main crust mineral. But you surely can't say that it's the main element of a planet.

Actually IIRC olivine is a major constituent mineral in Earth's mantle.
http://mineral.galleries.com/minerals/s ... livine.htm

It's rather seldom on earth surface because it oxidates fast when getting in contact with oxygen.

It's usually not hugely common on Earth's surface nowadays mostly because it's rare for it to be erupted up here, but you can find it in gabbros and kimberlites and ophiolites, and anywhere that mantle material has been brought up to the surface (eg Cyprus).

And Olivine doesn't react with oxygen - it reacts with water to form serpentine, that it's usually not a particularly fast reaction.

[maxim]

Grin ,

I should really take a short look into my references before making statements out of my weak memory:

Yes, of course it's a main component of the upper mantle, not the crust. And it reacts by chemical weathering not oxydation. Its seldom on the surface compared to the total amount of it in our planet. Of course you always get some by magmatic events or inside basalt formations. But it weathers rather fast compared to other minerals or stones like granite, limestone etc. (more of thousands of years instead of millions).

maxim