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| Titel |
Assessment of a Possible Volcanic Paleolake at Apollinaris Patera, Mars: Constraints on the Composition of the Inner Caldera and Fan Deposits using the MRO Shallow Sounding Radar (SHARAD) |
| VerfasserIn |
Mohamed Ramy El Maarry, Essam Heggy, James Dohm |
| 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 |
250047822
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| Zusammenfassung |
| Mars displays an abundance and great diversity of features that point to a long history of
water and volcanic activity, including widespread hydrothermal activity. Many localities,
mainly within impact basins, show evidence of lakes [1,2]. Studying such lakes is a key
element in the understanding of the geologic evolution of Mars in addition to being primary
targets for future exobiological exploration [3]. Lakes on Mars have been mainly attributed to
a wetter ancient climate, including precipitation [4], magmatic-driven flooding [5], or
impact-generated aqueous activity, including hydrothermal systems [1]. However, a lake
occupying a volcanic caldera has never been detected despite the fact that they are commonly
associated with magmatic/hydrothermal systems on Earth. In this work, we explore the
hypothesis that a volcanic paleolake existed in the caldera of Apollinaris Patera (174.4Ë E,
9.3Ë S) and has been responsible for the formation of extensive fan deposits that extend
approximately 150 km down the southern flank of the volcano from summit to base [6] using
data from the shallow sounding radar SHARAD [7] onboard the Mars Reconnaissance
Orbiter (MRO).
We have devised a "calibration" technique to compare between the relative
surface reflectivity and signal decay losses in the calderas of Apollinaris caldera
and Arsia Mons (9.2Ë S, 239.6Ë E); a site of known volcanic composition with
similar surface roughness. We chose Arsia Mons for calibration purposes since
its caldera has similar dimensions to those of Apollinaris and a relative age that
suggests volcanic activity from Late Noachian/Early Hesperian to as recent as 40 Mya
[8,9].
Our preliminary analysis shows that Arsia caldera surface displays a single bright and
continuous reflection suggesting the presence of a higher surface dielectric contrast that can
be attributed to volcanic material. This is also supported by the rapid signal decay due to the
strong dielectric attenuation. In the case of Apollinaris, however, the caldera displays two
types of reflecting surfaces that are not as bright as the one in Arsia which suggests that the
material in the Apollinaris caldera is not similar to that of Arsia and displays a lower
dielectric contrast.
Comparative surface roughness, clutter forward modelling, estimates of the
dielectric properties for the materials and radiometric data analysis of these two caldera
fills will be presented in detail at the meeting in addition to the results for the fan
deposits.
References:
[1] Newsom H.E. et al., (1996), JGR, 101, 14951-14956. [2] Cabrol N.A. and Grin E.A.
(1999), Icarus, 142, 160-172. [3] Newsom H.E et al., (2001), Astrobio., 1, 71-88. [4]
Mangold, N., Ansan, V., (2006), Icarus, 180, 75-87. [5] Fairén, A.G., et al., (2003), Icarus,
165, 53-67. [6] Ghail R. C. And Hutchison J. E., (2003), LPSC XXXIV, abstract #1775. [7]
Seu R. et al., (2007), JGR, 112, doi: 10.1029/2006JE002745. [8] Hartmann W.K. et al.,
(1999), Nature, 397, 586-589. [9] Mouginis-Mark P., and Rowland S.K., (2008), Icarus, 198,
27-36. |
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