Headquarters, Washington, DC July 7, 1999
NASA SELECTS MISSIONS TO MERCURY AND
A COMET'S INTERIOR AS NEXT DISCOVERY FLIGHTS
The first comprehensive mission to map pockmarked Mercury and
a radical mission to excavate the interior of a comet have been
selected as the next flights in NASA's Discovery Program.
The Mercury Surface, Space Environment, Geochemistry and
Ranging mission, or Messenger, will carry seven instruments into
orbit around the closest planet to the Sun. It will send back the
first global images of Mercury and study its shape, interior and
magnetic field. Dr. Sean Solomon of the Carnegie Institution,
Washington, DC, will lead Messenger.
The Deep Impact mission will send a 1,100-pound (500-
kilogram) copper projectile into comet P/Tempel 1, creating a
crater as big as a football field and as deep as a seven-story
building. A camera and infrared spectrometer on the spacecraft,
along with ground-based observatories, will study the resulting
icy debris and pristine interior material. Dr. Michael A'Hearn
will lead Deep Impact from the University of Maryland in College
"These low-cost missions are both fantastic examples of the
creativity of the space science community," said Dr. Edward
Weiler, associate administrator for space science at NASA
Headquarters in Washington, DC. "Messenger is a flagship-quality
effort that, in tandem with a separate Pluto mission, enables us
to seize the opportunity to complete our historic initial
reconnaissance of the Solar System. Deep Impact presents a
special chance to do some truly unique science, and it is a direct
complement to the other two comet missions already in the
Messenger, to be launched in spring 2004, will be NASA's
first mission to Mercury since the Mariner 10 flybys in 1974 and
1975, which provided information on only half the planet. Its
challenging flight plan begins with two Venus flybys, then two
Mercury flybys in January and October 2008 and a subsequent
orbital tour of Mercury beginning in September 2009.
Among Messenger's goals will be to discover whether Mercury
has water ice in its polar craters. The cost of Messenger to NASA
is $286 million. It will be built and managed by the Johns
Hopkins University's Applied Physics Laboratory, Laurel, MD.
Further information about the mission is available on the Internet
Deep Impact will be launched in January 2004 toward an
explosive July 4, 2005, encounter with P/Tempel 1. It will use a
copper projectile because that material can be identified easily
within the spectral observations of the material blasted off the
comet by the impact, which will occur at an approximate speed of
22,300 mph (10 kilometers per second.) The total cost of Deep
Impact to NASA is $240 million. Deep Impact will be managed by
NASA's Jet Propulsion Laboratory in Pasadena, CA, and built by
Ball Aerospace in Boulder, CO.
NASA selected these missions from 26 proposals made in early
1998. The missions must be ready for launch no later than Sept.
30, 2004, within the Discovery Program's development cost cap of
$190 million in Fiscal 1999 dollars over 36 months and a total
mission cost of $299 million.
The Discovery Program emphasizes lower-cost, highly focused
scientific mission. NASA has developed six other Discovery Program
missions. Two have completed their primary missions, two are
operational and two more are under development:
-- The Lunar Prospector orbiter has mapped the Moon's
composition and gravity field for the past 18 months. It will
complete its highly successful mission on July 31, when it is sent
on a controlled impact into a crater near the south lunar pole.
Scientists hope to observe a resulting plume of water vapor that
would help confirm the presence of water ice in some of the Moon's
permanently shadowed craters. In 1997, the Mars Pathfinder lander,
carrying a small robotic rover named Sojourner, landed
successfully on Mars and returned hundreds of images and thousands
of measurements of the Martian environment.
-- The Near Earth Asteroid Rendezvous (NEAR) spacecraft is
scheduled to enter orbit around the asteroid Eros in February
2000, after a problem with its initial attempt to do so early this
year. The Stardust mission to gather samples of comet dust and
return them to Earth was launched in February 1999.
-- The Genesis mission to gather samples of the solar wind
and return them to Earth and the Comet Nucleus Tour (CONTOUR)
mission to fly closely by three comets are being prepared for
launch in January 2001 and June 2002, respectively.