Astronomers hunt Martian water from Earth
As Mars makes its closest approach in almost 60,000 years, two Australian
astronomers have used the United Kingdom Infrared Telescope (UKIRT) in Hawaii to
look for signs that the planet once had liquid water — and so may have hosted life.
Dr. Jeremy Bailey of the Anglo-Australian Observatory and the Australian Centre
for Astrobiology (ACA) at Macquarie University in Sydney, and Sarah Chamberlain,
a PhD student at the ACA, have produced what is Bailey says is "perhaps the
sharpest image of Mars ever made from the ground."
But the real gold lies in the spectral data they obtained.
The scientists are applying the same remote-sensing technique that geologists
use to map minerals on the Earth’s surface.
Minerals absorb some wavelengths from sunshine and reflect others. Each mineral
has its own ‘spectral signature’ — the set of wavelengths it reflects.
"We’re looking particularly for the signatures of minerals, such as hydrated
clay minerals, that would indicate the past presence of liquid water," said Bailey.
Similar prospecting by NASA’s Mars Odyssey spacecraft has shown that there is a
vast amount of hydrogen below the surface of Mars. The consensus has been that
this is probably water ice.
But did Mars ever have liquid water? And if so, how much? It’s still contentious.
NASA’s Mars Global Surveyor has found sizeable deposits of a mineral called
crystalline (grey) hematite, which forms only in the presence of liquid water.
NASA’s two Mars Exploration Rovers, due to land on the Martian surface in
January 2004, and the UK lander Beagle 2, due to land in December this year,
will also be looking for signs that Mars has had liquid water.
"While spacecraft can get up close, ground-based observations still have a role,
as they allow us to use larger and more powerful instruments," said Bailey.
IMAGES
UKIRT image of Mars at infrared wavelengths
http://outreach.jach.hawaii.edu/pressroom/2003_mars/mars_colour_inv.jpg
(plain image, 106KB)
http://outreach.jach.hawaii.edu/pressroom/2003_mars/mars_annotated.jpg
(features annotated, 60KB)
The dark markings resemble those seen at visible wavelengths, but the south
polar cap (at the bottom of the picture) is less prominent as its ice absorbs at
infrared wavelengths. The slight green colour around the polar cap is a result
of ice absorption.
The image was obtained with the UIST (UKIRT imager spectrometer) instrument on
the 3.8-m United Kingdom Infrared Telescope (UKIRT). It is a composite of three
narrowband-filter images at wavelengths of 1.57, 1.64 and 2.12 micrometres in
the near infrared.
Observations: Jeremy Bailey (Anglo-Australian Observatory and Australian Centre
for Astrobiology, Macquarie University) and Sarah Chamberlain (Australian Centre
for Astrobiology, Macquarie University). Data processing: Chris J. Davis, Joint
Astronomy Centre, Hawai’i.
UKIRT
The United Kingdom Infrared Telescope. Credit: Nik Szymanek
http://outreach.jach.hawaii.edu/pressroom/2003_mars/ukirt.jpg (2.3MB)
The United Kingdom Infrared Telescope at night with star trails. Credit: Nik
Szymanek
http://outreach.jach.hawaii.edu/pressroom/2003_mars/ukirttrails.jpg (184KB)
Notes for editor:
UKIRT
The world’s largest telescope dedicated solely to infrared astronomy, the
3.8-metre UK Infrared Telescope (UKIRT) is sited near the summit of Mauna Kea,
Hawaii, at an altitude of 4194 meters above sea level. It is operated by the
Joint Astronomy Centre in Hilo, Hawaii, on behalf of the UK Particle Physics and
Astronomy Research Council.
UIST
The UKIRT Imager Spectrometer (UIST) was designed and built at the UK Astronomy
Technology Centre (UK ATC) in Edinburgh. It detects infrared light at
wavelengths between 1 and 5 microns with a 1024 x 1024 pixel Indium Antimonide
detector array. It can be used for imaging, spectroscopy, integral field
spectroscopy, and polarimetry. It cost just under UKP 3M to build and was funded
by the Particle Physics and Astronomy Research Council (PPARC).
Web links
* Joint Astronomy Center
http://outreach.jach.hawaii.edu/
* Australian Centre for Astrobiology
http://aca.mq.edu.au/
* Anglo-Australian Observatory
http://www.aao.gov.au/
