2010 Lunar and Planetary Science Conference abstracts are up

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March 1–5, 2010
http://www.lpi.usra.edu/meetings/lpsc20 ... rogram.pdf

Here's an interesting one I found:

A. Johnsson1, L. Johansson1, M. Zanetti2, D. Reiss2, E. Hauber3, H.
Hiesinger2, R. M. Ulrich4, M. Olvmo1, E. Carlsson5, R. Jaumann3, F. Trauthan3, F. Preusker3, H.A.B. Johansson6, and S.

Near the end of their abstract, the authors do raise the possibility that freeze-thaw cycles under the present atmospheric regime could be possible and are the origin of these stripe-like patterns. But at the beginning they state:

"Due to the current
temperature and pressure regime on Mars soil
moisture and active layer processes are not likely to
occur [4]"

which rather implies at the start they don't expect this to be the likely answer.

However, I looked at the cited report by Kreslavsky and Head and found what they calculate is the average temperature according to latitude and obliquity on Mars:

M. A. Kreslavsky1,2, and J. W. Head1.
"Introduction: Estimation of the summer dayaverage
surface temperature on inclined surfaces on
Mars has been done in [1] with a global climate model
(GCM) for different obliquities. These calculations
showed that starting from ~35° obliquity, the maximal
day-average temperature reaches the ice melting point
at high latitudes; for even higher obliquity, the dayaverage
temperature exceeds 0°C at lower latitudes, up
to 40° latitude at 45° obliquity, but only at 20-30°-
steep pole-facing slopes."

This is a real sore point with me. I have found that quite often Mars scientists when they want to argue against the possibility of liquid water on present day Mars, they will always talk about the lowest temperatures or the average temperature on Mars, when clearly it should be the *maximum* temperature that should be mentioned. I discussed this in a post to sci.astro copied below.
Then given the fact that several recent observations have shown current ground ice, perhaps with a thin dust cover, from mid latitudes down to even near equatorial latitudes on Mars, a more useful calculation would be towards how long the temperatures stay above zero at particular latitudes and how much liquid ground water would be expected to be produced given the observed amounts of ground ice at those latitudes. As a starting point towards that, here's an article that did calculate when the maximum temperature is above the melting point of water on present day Mars:

Use of spacecraft data to derive regions on Mars where liquid water would be stable.
Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 5, 2132-2137, February 27, 2001

Could the amount of current ground water generated produce the young gullies and larger channels found on Mars *in current times*?

Bob Clark

Newsgroups: sci.astro, alt.sci.planetary, alt.astronomy, sci.geo.geology, sci.astro.amateur
From: rgregorycl...@yahoo.com (Robert Clark)
Date: 23 Mar 2002 06:08:57 -0800
Local: Sat, Mar 23 2002 9:08 am
Subject: Mars temperatures - they're doing it again!

Probably most regular readers of sci.astro know by now my view on the
temperatures on Mars and the possibility of liquid water on the Red
Planet, cf.,

From: Robert Clark (rgcl...@my-deja.com)
Subject: NASA proving Levin's theory right about liquid water on Mars?
Newsgroups: sci.astro, sci.space.policy, sci.astro.seti, sci.physics
Date: 2000-11-19 10:10:10 PST
[Expired link. Try instead: http://groups.google.com/group/sci.astr ... 94466ef4ca]

A real pet peeve of mine is that *usually* scientists cite the
lowest temperatures or average temperatures on Mars to conclude that
liquid water can not exist on Mars.
My view is that a more relevant temperature to give is the maximum
temperature on Mars. I'm fairly certain for example that the average
temperature in Fairbanks, Alaska is below zero Celsius, but would you
conclude then from that that liquid water can not exist in Fairbanks,
Alaska? (BTW, here's an image of the Chena River in Fairbanks:
http://www.dashdeli.com/photos.shtml )
[Expired link. Try instead: http://cache.virtualtourist.com/1618222 ... rbanks.jpg]

This occurred again in regards to the recent announcement of the
results from Mars Odyssey indicating large amounts of water in the
southern hemisphere:

Odyssey Finds Large Concentrations of Water on Mars.
"The scientists know that the water is ice rather than liquid,
because the temperatures on Mars are well below freezing. The average
temperature of Mars is –63 C (–81 F) and the instruments of Odyssey
indicate the coldest temperature in the Southern Hemisphere right now
is -101 C (–150 F).
"It's just too darn cold for it to be liquid water,' says Boynton."
[Expired link. Try instead: http://nai.nasa.gov/news_stories/news_detail.cfm?ID=22]

What's interesting here is that they refer to Odyssey instruments
giving this coldest temperature. Yet there was an infrared image
released from the THEMIS infrared imager on Odyssey showing above
zero temperatures being reached in the southern hemisphere of Mars:

First THEMIS Infrared and Visible Images of Mars.
http://mars.jpl.nasa.gov/gallery/polari ... 03461.html

Also, the TES imager on Mars Global Surveyor has shown that
temperatures can exceed 20 C as far south as 60 S latitude:

http://wwwflag.wr.usgs.gov/USGSFlag/Spa ... ole99.html
[Expired link. Try instead: http://www.mars-ice.org/_more/about/sp99.php]

Since the Odyssey infrared imager has a better resolution than the
TES instrument, I presume the THEMIS instrument would confirm this as

Bob Clark


Thanks Bob, I will read your links properly later. Already there is much of interest there. Quite a surprise to see that it can get so warm that far south!!!

Some other abstracts that have grabbed my interest. Planet Mercury & Asteroid 4 Vesta.


MESSENGER'S THREE FLYBYS, an emerging view of the innermost planet.
Introduction: The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, launched in August 2004 under NASA’s Discovery Program, will be the first probe to orbit the planet Mercury. MESSENGER’s three flybys of Mercury, the most recent on 29 September 2009, marked the first spacecraft visits to the innermost planet since
those of Mariner 10 in 1974-1975 [1]. Her...

Measurements of Neutron Absorbing Elements on Mercury from the Three MESSENGER Flybys.
Introduction: Despite many measurements from Earth and from the Mariner 10 spacecraft, there is little definitive information about the elemental composition of Mercury’s surface [1]. Specifically, there has been
much debate about the Fe content of Mercury’s surface materials [2,3]. For example, 1-μm absorption bands
resulting from Fe2+ in silicates are either absent or very weak in reflectance spectra of Mercury at visible to
near-infrared wavel....

Mercury Radii from MESSENGER Flyby Occultations.
Introduction: The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has completed three flybys of Mercury [1]. During the first (M1) and third (M3) flybys, MESSENGER passed behind Mercury when viewed from the Earth, occulting the radio-frequency (RF) transmissions. Combined with accurate ephemeris, the times of the RF occultations provide estimates of the planet radius at the surface location tangent to the grazing ray. T...

The MESSENGER spacecraft completed its third and final flyby of Mercury on 29 September 2009 and is now en route to orbit insertion on 18 March 2011 [1]. During the approach to that flyby, imaging filled in a further 6% of the Mercury global map. The MESSENGER spacecraft has now imaged ~91% of Mercury’s surface; including Mariner 10 data, ~98%
of the planet has now been imaged by spacecraft. The new MESSENGER images reveal a multi-ring impact basin located at 27.4º N, 57.6º E, measuring 290 km in diameter (Fig. 1). In terms of size and morphology, the basin closely resembles the 265-km diameter Raditladi double-ring basin that was imaged during MESSENGER’s first Mercury flyby [2, 3] (inset, Fig. 1). The new b....

The Morphology of Craters on Mercury: Results from the MESSENGER Flybys.
Introduction: Topographic profiles obtained by the Mercury Laser Altimeter (MLA) and stereo topography and shadow-derived estimates of topography from the Mercury Dual Imaging System (MDIS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft were used for investigations of the relationship between depth and diameter for impact craters on Mercury. The data provide new observational constraints on factors that might i...

AGE Determination of Raditladi and Rembrandt Basins and Related Geological Units.
Introduction: MErcury Surface, Space ENviron-ment, Geochemistry and Ranging (MESSENGER) spacecraft was designed to visit Mercury after the long silence that follows Mariner 10 call on this planet. During these last two years, MESSENGER took three gravity assists with the planet, providing a great deal of information, first of all an extensive imaging of a portion of Mercury’s surface never seen before. Two examples are Raditladi (27°N, 119°E), revealed during the first fly-by, and Rembrandt (33°N, 88°E), during the second. In this work, we analyz.....

Testing Mechanisms for the Formation of a Ring of Graben in Central Raditladi Basin, Mercury.
Introduction: Observations of Mercury’s surface by the MESSENGER spacecraft reveal a planet dominated by contractional tectonic features, most notably widespread lobate scarps [1] caused by surface contraction associated with interior cooling [2, 3]. Evidence of extensional faulting on Mercury is rare, primarily restricted to the floors of a few impact basins. One of these is the 250-km-diameter Raditladi basin, which was first imaged by the MESSENGER spacecraft during its first flyby (Fig. 1a) [4]. Evidence for extension within Raditladi is in the form of tr.....

Mechanical Structure of Mercury’s Lithosphere from MESSENGER Observations of Lobate Scarps.
Introduction: Laser ranging during the first two of three flybys completed by the MESSENGER space-craft at Mercury have detected a variety of landforms interpreted to be the result of contractional tectonics, including a number of lobate scarps and wrinkle ridges [1,2]. The Mercury Laser Altimeter (MLA) has ob-served relief over these scarps in excess of 1 km, indi-cating a significant amount of contractional strain ac-commodation at the surface. Lobate scarps have been detected over most of the planet and are amo....

Classification of MESSENGER MASCS Data.
Introduction: The MESSENGER spacecraft flew by Mercury as part of its journey to Mercury orbit insertion. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) [1,2] observed Mercury during two flybys, including high-spatial-and spectralresolution visible to near-infrared (IR) spectra of the Mercury surface. The Visible and InfraRed Spectrograph (VIRS) component of MASCS consists of two linear photo.....

Emerging Perspectives on Mercury’s Internal Structure from MESSENGER Flyby Observations and Geophysical Modeling.
Introduction: New observations by the MESSENGER spacecraft during its three flybys of Mercury [1] have revealed that the innermost planet preserves a geological record of extended interior activity [2]. Distributed and impact-basin-related tectonics [3-5] and abundant volcanism [6-7] point to active mantle and lithospheric dynamics throughout much of
the planet’s history [cf. 8-10]. Study of the current internal structure and past plausible structures provide constraints on Mercury’s internal dynamics over time that can be linked to the surface record. Geophysical
observations from MESSENGER coupled with modeling are contributing to impro....

Constraints on the Internal Structure of Mercury After Three MESSENGER Flybys.
Introduction: A persistent issue in our under-standing of the formation of the terrestrial planets has been the enigmatically large bulk density of Mercury of 5430 kg m-3 [e.g., 1]. A bulk density this large implies that the mass fraction of iron in Mercury’s interior is considerably greater than in the other terrestrial pla-nets. Data available to date have not permitted the opportunity to robustly estimate Mercury’s internal structure. However, much recent work has focused on understanding how measurements to be made by MESSENGER and BepiColombo will constrain know-ledge of Mercury’s in.....

Now to Asteroid 4 Vesta with DAWN.

Exploring Asteroid 4 Vesta with the Dawn Mission
Introduction: The ion-propelled Dawn spacecraft entered the asteroid belt on November 13 after gaining a gravity assist from Mars on February 19, 2009. It will begin orbiting Vesta in August of 2011, after spending roughly three months approaching the protoplanet, being captured, and achieving the desired science orbit. Dawn will spend roughly one year orbiting Vesta and collecting data in three orbit subphases. The Survey orbit is at 3000 km radius, the High Altitude
Mapping Orbit (HAMO) is at 950 km radius, and the Low Altitude Mapping Orbit (LAMO) is at 460 km radius. The spacecraft arrives at Vesta during austral summer (Southern Summer on 4 Vesta) and dep....

SHAPE Modeling of 4 Vesta for Dawn Mission Support and SHAPE Inversion Validation.
Introduction: Vesta was chosen as a target by the Dawn mission for its unique physical properties and the insight it can offer into the planetary formation process. Considered by some to be a protoplanet, it is thought to be the only asteroid with a differentiated, intact internal structure [1] (with the possible exceptions of 1 Ceres & 2 Pallas). The second most massive object in the asteroid belt, it is believed to be the source of HED (Howardite, Eucrite, Diogenite) m....

Rotationally-resolved Compositional Study of Asteroid 4 Vesta’s Southern Hemisphere: Implications for the DAWN Mission.
Introduction: Vesta is the largest basaltic asteroid that remains mostly intact today and can be considered as a model for the early stages of planetary differentiation. Vesta has been postulated (e.g., 1, 2 and 3) as the parent body of the HED (howardite, eucrite, and diogenite) meteorites based on their similar near-infrared (NIR) spectra. A small cluster of asteroids (D <10 km) has been ide......

Impacts on 4 Vesta.
We present 3D SPH simulations of impacts on asteroid 4 Vesta, the 540-km diameter differentiated target of NASA’s Dawn mission. Because Vesta is a low-gravity ( 1/30G) body that is likely to be, certainly after a hemispheric impact,
highly fragmental, we include a new model to simulate the granular flow of post-impact regolith. We assume an iron
core and three different mantle rheologies (solid, strengthless, granular) and central gr.....

Giant Impacts Can Drive Asteroid Dynamics: Lessons for 4 Vesta.
Introduction: Hubble Space Telescope imaging revealed that the south pole of Vesta is characterized by a large basin 460 km in diameter and ~ 13km deep[1]. Variations in reflectance and composition across Vesta, have been attributed to the exposure of deep crustal and possibly mantle materials, and its spectral link to the HED meteorites further suggests that Vesta was differentiated prior to th....

Are the Spin Poles of 1 Ceres and 4 Vesta Fully Damped?.
Introduction: We examine models of secular variations in the orbit and spin poles of 1 Ceres and 4 Vesta, the two most
massive bodies in the main asteroid belt. If the spin poles are fully damped, then the current values of obliquity, or angular separation between spin and orbit poles, are diagnostic of the moments of inertia and can be used together with gravity measurements to determine the extent of differentiation of these bodies. Using existing shape models and assuming unif....

Andrew Brown.


thanks andrew for the info.
I jumped of course immediately on your link for Ceres and Vesta spin poles damping and was elated to see that the authors conclude that the damping assumption is reasonable for both Ceres and Vesta, supporting in turn the assumption of a high degree of differentiation. This was expected for Vesta. For Ceres, this is a stone in the garden of the anti-water, anti-differentiation, pro-porous camp.

I will continue to read the abstracts.

Best regards.
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