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Past Speakers
“The Role of Water on Mars: Interpretations Through the Eyes of a Geologist”
Dr. Phil Christensen
Arizona State University
Thursday, September 22, 2005
Building 245 Main Auditorium
Tea & Cookies at 3:30pm (2nd floor lobby area)
Colloquium at 4:00pm
Point of Contact: yibarra@mail.arc.nasa.gov
Abstract
Our understanding of the role of water throughout Mars' history has changed dramatically over the past 30 years, and continues to be a topic of intense investigation. A fleet of orbiting and roving spacecraft has explored Mars over the past decade, and has provided a vast amount of new information that has greatly expanded the debate about the climate and environment of Mars, its evolution over time, the history of water, and possibility that life could have originated. The ancient rocks sitting at the surface of Mars were formed in the early environment, and have been exposed to all of the changes that have since occurred. As a result, the geologic record provides an excellent starting point for unraveling the history of water on Mars. The Mars Exploration Rovers have provided detailed chemical, mineralogical, and morphologic evidence for aqueous alteration in surface or near-surface systems of standing water. Global mineral maps from the orbiting Mars Global Surveyor, Mars Odyssey, and Mars Express spacecraft show that Mars is dominated by volcanic processes, but has localized occurrences of minerals formed by aqueous processes. These observations present conflicting views - Mars abounds with river channels, yet volcanic minerals that would quickly break down in a wet environment are present in very old terrains; the current climate is very dry and cold, yet the Opportunity rover landed on the floor of an ancient playa; liquid water cannot exist today, yet recent gullies are common throughout the mid-latitudes. The emerging picture is one of a complex planet - not a simple view of "warm and wet" versus "cold and dry" - but that of a real world on which relative importance of physical and chemical weathering may differ significantly from that of the Earth, and where the abundance and impact of water has changed dramatically through space and time.
Biography
Philip R. Christensen is a Regents Professor and the Ed and Helen Korrick Professor in the Department of Geological Science at Arizona State University. He joined Arizona State University following the completion of his Ph.D. in Geophysics and Space Physics at UCLA in 1981. His research interests focus on the composition, physical properties, processes, and morphology of planetary surfaces, with an emphasis on Mars and the Earth. A major element of his research has been the design and development of spacecraft infrared remote sensing instruments. Christensen is the Principal Investigator for the 2001 Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument, and the Thermal Emission System (TES) instrument on Mars Global Surveyor. He is also a Co-Investigator on the Mars Exploration Rover missions, responsible for building and operating the Mini-TES instruments. His research uses infrared spectroscopy, radiometry, laboratory spectroscopic measurements, field observations, and numerical modeling, and has taken him to field sites in the western U.S., Hawaii, Mexico, and South America. Since the mid-1990's he has pursued the use of spacecraft observations to study environmental and urban development problems on Earth. Christensen was awarded NASA's Exceptional Scientific Achievement Medal in 2003 for his pioneering scientific observations of Mars in the infrared, and was elected as a Fellow of the American Geophysical Union in 2004.
On Wednesday, September 14, 2005, Dr. Sun Kwok of the Institute of
Astronomy & Astrophysics, Academia Sinica, Taiwan
will present a Colloquium
at 4:00pm in the Building 245 Main Auditorium entitled "Planetary
Nebulae: Their evolution and role in the universe." All staff are
cordially invited to attend.
Abstract
Although planetary nebulae (PNe) have been known for over 200 years,
a theoretical understanding of the origin and evolution of these
objects only began 30 years ago. Recent observations in the x-ray,
ultraviolet, infrared, submm and mm regions show that PNe are active
throughout the electromagnetic spectrum and are excellent
laboratories for the study of atomic and molecular processes.
Observations by the HST have discovered FLIERS, knots, jets, arcs,
rings, and point-symmetric structures that are difficult to explain.
ISO observations have discovered many inorganic and organic
compounds, some of which have been found in presolar grains in the
solar system. The detection of extragalactic PNe also allows them to
be used as a standard candles for extragalactic distance scales,
probes of distribution of dark matter, as well as tools to study the
dynamic history of galaxy clusters. A modern understanding of PNe is
therefore important for the study of the solar system, stellar
evolution, interstellar medium, galactic structure and evolution as
well as cosmology.
Dr. Ewine F. van Dishoeck
Leiden Observatory, The Netherlands
will give the next Space Science and Astrobiology Colloquium on
“Ice cold and steaming hot Spitzer observations
of gas and dust in star- and planet-forming regions”
Thursday, August 25, 2005
Building 245 Main Auditorium
Tea & Cookies at 3:30pm (2nd floor lobby area)
Colloquium at 4:00pm
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