Observing the Solar System in Submillimeter Wavelengths

http://www.cfa.harvard.edu/press/pr0519.html

Harvard-Smithsonian Center for Astrophysics
Release No.: 05-19
For Release: Thursday, June 16, 2005

Note to editors: A high resolution image to accompany this release is
online at http://www.cfa.harvard.edu/press/pr0519image.html.

Observing the Solar System in Submillimeter Wavelengths

-- Getting Ready to Fingerprint a Comet --

Cambridge, MA--The Submillimeter Array (SMA) will be ready and watching
when NASA's Deep Impact probe strikes the nucleus of Comet Tempel 1 on
July 4th. The impact is expected to excavate material from the comet's
interior - material left over from the earliest days of our solar
system.

"The SMA will be the only operational millimeter or submillimeter array
observing Tempel 1 at the time of the impact" said astronomer Charlie
Qi
of the Harvard-Smithsonian Center for Astrophysics (CfA). "As such,
there's no telling what we may see!"

Only a few observatories can study comets in the same wavelength regime
as the SMA, but none match SMA's exquisite resolution. "The SMA will be
the only submillimeter telescope in the world to make an image of the
molecules released by the impact," said Glen Petitpas (CfA).

By observing submillimeter radiation, the SMA can "fingerprint" comets
and determine their molecular composition. "SMA will observe mostly
cool
gas and dust with relative chemical abundances that may or may not be
typical of other comets. We hope to see something NOT typical, because
that would be most exciting to us scientifically," said Qi.

In the 1950s, the late Dr. Fred Whipple (CfA) developed the famous
"dirty snowball" model for comets. Whipple hypothesized that comets
consisted of ice with some dirt and rock mixed in. Modern astronomers
believe that comets are better described as "icy dirtballs," containing
more dirt and less ice than previously thought.

Deep Impact's mission is to test these new models by excavating a
crater
more than 80 feet deep and 300 feet in diameter, revealing the comet's
pristine interior. Scientists will compare the freshly excavated
material to the more easily visible cometary surface.

Ernst Tempel discovered Comet Tempel 1 in 1867. The comet has made many
passages through the inner solar system orbiting the Sun every 5.5
years. This makes Tempel 1 a good target to study evolutionary change
in
the mantle, or upper crust, of the comet.

While the impending SMA observations of Deep Impact were a hot topic of
discussion at this week's meeting on submillimeter astronomy held in
Cambridge, Mass., Comet Tempel 1 is only one of the solar system
objects
that the SMA has studied.

-- Monitoring the Weather on Mars --

The planet Mars also has been a target of particular interest. As
rovers
and orbiters study the Red Planet close-up, the SMA takes in the big
picture from a distance.

"Our research is very complementary to the spacecraft exploring Mars,"
said astronomer Mark Gurwell (CfA). "We get a large-scale picture in a
different way from the Mars Global Surveyor, for example."

While missions to Mars have focused mainly on the planet's surface, the
SMA is sensitive to conditions within the planet's atmosphere. As such,
it serves as an Earth-based weather station, able to monitor
atmospheric
conditions on Mars from millions of miles away.

"The SMA enables us to study abundances of molecules and thus
atmospheric chemistry. We can study atmospheric dynamics of an entire
hemisphere at a time," said Gurwell. "Our measurements give us a 3-d
map
of atmospheric temperatures to greater heights than any Mars-orbiting
spacecraft can measure. We can go higher, and we can monitor the planet
throughout the Martian day."

-- Investigating the Atmosphere of Titan --

Gurwell also uses the SMA to measure the upper atmospheric temperature
of Saturn's moon Titan. Before the Cassini spacecraft reached the
Saturnian system, Gurwell was studying Titan to learn more about this
enigmatic moon, whose surface is shrouded by its thick, hazy
atmosphere.

"We saw large gradients of hydrogen cyanide and other chemicals between
the northern and southern hemispheres," said Gurwell. "These gradients
tell us about the climate and dynamics of the atmosphere. Plus, since
Titan is an analog to the early Earth, we can use our measurements of
Titan to start to extrapolate what conditions were like on the Earth
four billion years ago, just before life developed."

Continued SMA observations will provide useful information about
seasonal weather patterns on Titan, where a `year' is nearly 30 Earth
years long.

"If we develop an understanding of Titan's climate and seasonal
changes,
we may be able to better understand how other atmospheres, including
the
Earth's, are affected by changes in seasons," Gurwell explained. "This
could become very important when we begin to study planets around other
stars."

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.

For more information, contact:

David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468


Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016