| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
03 May 2007 04:41:08 PM |
| Object: |
Mercury is Soft in the Middle |
Mercury is Soft in the Middle
http://www.universetoday.com/
A team of astronomers has discovered that tiny Mercury has a molten
core, just like our own planet. The discovery was made using three
ground-based radio observatories that bounced radio waves off the
planet, and then analyzed the return signals.
Before this research, scientists were divided about the structure of
Mercury. Most models predicted that it has an iron-rich core, but it
wasn't known if it had completely cooled, or was still liquid inside.
Trace quantities of sulfur and other chemicals could have mixed in
with the planet while it was forming, and this kept it from
completely solidifying over time.
The astronomers first beamed a series of radio waves at the surface
of Mercury, and then measured them as they bounced off the surface
and returned to Earth. The returned signals were analyzed by a trio
of radio telescopes: the Arecibo Observatory in Puerto Rico, NSF's
Robert C. Byrd Green Bank Telescope, and the NASA/JPL 70-meter
antenna at Goldstone, California.
They were able to detect a wobbling of the signal that was double
what you would expect from a planet with a solid core, but exactly
the right amount for a planet with a liquid core.
Their research is the cover story of the May 4, 2007 edition of the
Journal Science.
See: http://www.universetoday.com/
.
|
|
| User: "Sam Wormley" |
|
| Title: Re: Mercury is Soft in the Middle |
04 May 2007 09:57:45 AM |
|
|
Sam Wormley wrote:
Mercury is Soft in the Middle
http://www.universetoday.com/
Molten core solves mystery of Mercury's magnetic field
http://physicsweb.org/articles/news/11/5/7/1
4 May 2007
Being the closest planet to the Sun, you might think Mercury would be
the most likely rocky planet in the Solar System to have a molten
core, but for the past three decades physicists have not been quite
so sure. By taking radar measurements of Mercury using ground-based
radio telescopes, however, physicists in the US and Russia claim to
have proved that the variation in the planet's spin rate is indeed
characteristic of a molten core. Their work also lends weight to the
idea that Mercury, like Earth, produces its magnetic field in the
molten core through dynamo action (Science 316 710).
Despite its 400 °C surface temperatures, physicists originally
predicted that Mercury's small mass -- about 5% that of the Earth --
would have allowed its core to cool down enough to solidify long ago.
But their predictions became much less certain in the 1970s after
NASA's Mariner 10 spacecraft flew by the planet and detected a small
internal dipole magnetic field. Although some claimed that the field
could have been a fossil of an earlier one "frozen" into the crust,
others maintained that this was very unlikely, and that dipole
magnetic fields in terrestrial planets are normally a result of the
convection of molten iron producing a dynamo.
See: http://physicsweb.org/articles/news/11/5/7/1
.
|
|
|
|
|
Related Articles |
|
|
