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| Titel |
Thermophysical Properties of Selected Lunar Study Regions Determined from LROC and Diviner Data. |
| VerfasserIn |
Karin Bauch, Harald Hiesinger, Mark Robinson, Frank Scholten |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054555
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| Zusammenfassung |
| The thermal inertia of a surface is an important property for determining temperature
variations of planetary surfaces [e.g. 1, 2]. It represents the ability of a subsurface to retain
heat and is defined as a combination of thermal conductivity k, density Ï and heat capacity C.
Fine grained soil quickly looses heat during the lunar night, and therefore has a low
thermal inertia. Rocks and exposed bedrock store more heat during the night and
have higher thermal inertia values, which results in higher nighttime temperatures
[2].
Using Diviner temperature data combined with subsets of the 100 m grid LROC WAC
DTM (GLD100, [3]), we derived maps of thermal inertia for different study regions, such as
Taurus-Littrow Valley, Aristarchus and Lichtenberg Crater. Diviner nighttime temperatures
are used to estimate thermal inertia of the lunar surface. The data was binned in
one hour intervals, at a minimum resolution of 32 pixels per degree. We use an
expanded version of the thermal model presented by [4] to generate temperature curve
look-up tables for various thermal inertia values including different local topography,
layering, and time of the lunar day. For each surface facet, we compare measured and
modeled temperature data in order to find the best fitting thermal inertia value.
This approach is similar to martian thermal inertia derivations described by [2,
5].
Most of the area at Taurus-Littrow valley can be described by a layering subsurface
model, with a very fine regolith of ~ 2 cm having a low thermal inertia (~ 20 Jm-2K-1s-1-2
during the night) covering a more dense and conductive layer. This model is also in good
agreement with a model obtained for the Apollo temperature measurements as
described by [6]. The second layer on the floor of the valley has thermal inertia
values < 100 Jm-2K-1s-1-2 during the night. Due to the temperature dependence
of thermal conductivity and heat capacity, the values are higher during the lunar
day. The massifs surrounding the valley (Northern Massif, Sculptured Hills, and
Southern Massif) and impact craters have higher thermal inertia values (> 300
Jm-2K-1s-1-2).
Temperatures measured on the ejecta blanket of Aristarchus crater can also be explained
by a layered subsurface model. Thermal inertia decreases with distance from the crater,
indicating finer material with increasing distance. Close to the crater, thermal inertia of the
second layer is < 200 Jm-2K-1s-1-2, with increasing distance thermal inertia decreases to
less than 100 Jm-2K-1s-1-2.
The floor of the impact crater is 30-35 K warmer than the ejecta blanket. High
temperature anomalies are associated with the central peak, which is about 40 K warmer than
ejecta blanket. Parts of the crater wall, in particular in the north-east, are up to 60 K warmer
than the ejecta blanket. These areas suggest the presence of rocks and/or bedrock at or very
close to the surface. This is confirmed by high-resolution NAC-images, showing boulders of
different sizes in these regions.
The ejecta blanket of Lichtenberg crater also shows evidence for low thermal
inertia (< 100 Jm-2K-1s-1-2). As for Aristarchus, high temperature anomalies are
associated with the crater walls. However, temperatures on the crater floor and
walls are only 20 K and up to 40 K higher than the ejecta blanket, respectively.
Ejecta blankets of both craters do not show evidence for large boulders or exposed
bedrock.
References: [1] Urquhart, M.L. and Jakosky, B.M. (1997), JGR 102, 10,959-10,969. [2]
Mellon, M.T. et al. (2000), Icarus 148, 437-455. [3] Scholten, F. et al. (2011), LPSC XLII. [4]
Bauch, K.E. et al. (2009), LPSC XL, Abstract #1789. [5] Putzig, N.E. et al. (2005), Icarus
173, 325-341. [6] Keihm, S.J. and Langseth, M. G., Jr. (1973), Proc. Lunar Sci. Conf. 4,
2503-2513. |
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