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Topic Name: Explains New Theory Ice on Mars
Category: Nuclear
Research persons: Dr. Norbert Schörghofer , Mrs. Karen Rehbock
Location: Institute for Astronomy, 2680 Woodlawn Drive Honolulu, Hawaii 96822, United States
Details
Mars cause ice ages that are much more dramatic than those on Earth, says
astronomer Norbert Schörghofer of the University of Hawaii.
Thanks to our large, stabilizing Moon, Earth's rotation axis is always tilted
by about 23 degrees. The tilt of Mars, however, can wobble by as much as10
degrees from its current 25 degrees. Wobbles cause big changes in the amount of
sunlight reaching different parts of Mars, so vast amounts of ice shift between
the poles and the rest of the planet every 120,000 years.
Schörghofer's new theory appears in the September 13 issue of the journal
Nature.
"We expect to see two types of ground ice when the Phoenix Lander spacecraft
arrives at Mars in 2008," says Schörghofer, "ice that formed on the surface and
was then buried, and ice hidden in porous soil."
During the 19th century, scientists discovered that Earth experienced ice
ages. In the past few years, spacecraft have discovered that ice ages also
occurred on Mars, but scientists have been puzzled because more ice than
expected has survived far from the polar caps. What is left is now thought to be
a combination of old ice from the last major glaciation and younger ice that
formed later and in a way entirely different from the way ice formed on Earth.
The new theory sheds light on the history of vast ice-rich areas, which once
covered most of Mars. Around 4 to 5 million years ago, ice accumulated from
extensive snowfall outside the martian polar caps. The new theory describes what
happened to this ice as the rotation axis of Mars continued to wobble over the
last few million years.
Surface temperature and atmospheric humidity changed because of varying
sunlight. When the climate was dry, the ice receded to a greater depth or
disappeared entirely except at the highest latitudes. Dust contained in
retreating ice eventually covered the ice, making it no longer visible on the
surface.
So much of this subsurface ice has been detected that its only plausible
origin was thought to be massive snowfall. However, Schörghofer's theory
suggests that a lot of that snowfall ice has since been lost to the atmosphere.
It has been replaced by a new layer of ice, formed not from snowfall, since the
climate had meanwhile turned less humid, but by diffusion of water vapor into
the soil. Atmospheric vapor can freeze inside the soil and form "pore-ice,"
which is mainly soil with some ice in pore spaces.
As the planet's tilt toward the sun went back and forth, the climate kept
changing between dry and humid, causing many cycles of ice retreat and
formation. Today we are left with two kinds of ground ice: the old massive ice
sheet and very recent pore-ice.
Schörghofer is part of the multidisciplinary UH Astrobiology Institute, which
is sponsored by NASA and managed through the Institute for Astronomy. Its
research focuses on water as the habitat of, and chemical enabler for, life.
The NASA Astrobiology Institute (NAI), founded in 1998, is a partnership
between NASA, 16 major U.S. teams, and five international consortia. NAI's goal
is to promote, conduct, and lead integrated multidisciplinary astrobiology
research and to train a new generation of astrobiology researchers. For more
information, see http://nai.nasa.gov/.
Founded in 1967, the Institute for Astronomy at the University of Hawaii at
Manoa conducts research into galaxies, cosmology, stars, planets, and the sun.
Its faculty and staff are also involved in astronomy education, deep space
missions, and in the development and management of the observatories on
Haleakala and Mauna Kea.
About The Researcher
Dr. Norbert Schörghofer
Institute for Astronomy
University of Hawaii at Manoa
Honolulu, Hawaii 96822
Phone: 1-808-956-9086
Email: norb1@ifa.hawaii.edu
Mrs. Karen Rehbock
Assistant to the Director
Institute for Astronomy
University of Hawaii at Manoa
Phone: 1-808-956-6829
Email: rehbock@ifa.hawaii.edu
Astrobiology
Astrobiology is an emerging field, and still a developing subject, the
question of whether life exists elsewhere in the universe is a verifiable
hypothesis and thus a valid line of scientific inquiry. Astrobiology is a
multidisciplinary field utilizing physics, biology, and geology as well as
philosophy to speculate about the nature of life on other worlds. One
commentator on the field, planetary scientist David Grinspoon, calls
astrobiology a field of natural philosophy, grounding speculation on the unknown
in known scientific theory (Grinspoon 2003). Since we have only one example of a
planet with life (the Earth), most of the work is speculative and based on
current understanding of physics, biochemistry, and biology.
Though once considered outside the mainstream of scientific inquiry,
astrobiology has become a formalized field of study. NASA now hosts an
Astrobiology Institute. Additionally, a growing number of universities in the
United States (e.g., University of Arizona, Penn State University, and
University of Washington) Canada, Britain, and Ireland now offer graduate degree
programs in astrobiology.
Related Online Recourses
http://news.bbc.co.uk/1/hi/sci/tech/2013114.stm
http://www.allaboutspace.com/subjects/astronomy/glossary
http://www.newscientist.com/article.ns?id=dn7039
http://www.psrd.hawaii.edu/June02/MarsGRSice.html
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