A team of researchers partnered with the NASA Lunar Science Institute (NLSI) has developed a new hypothesis for the origin of crater ejecta—debris that is launched out of a crater during meteorite impacts.

These findings may help scientists target samples for extraction during future missions to asteroids and terrestrial bodies such as Mercury, Venus, the moon and Mars. The results are published in the Sept. 21, 2011, issue of the Elsevier journal, Earth and Planetary Science Letters.

The science team, led by professor Gordon Osinski at The University of Western Ontario, London, Ontario, compared observations of ejecta from all terrestrial planets. The observations showed that ejecta deposits all contained more than one layer.

“Understanding ejecta is critical for understanding the context of samples collected by humans and robots during previous missions and may aid in targeting future sample return missions to the moon, Mars and beyond,” said Osinski.

Craters formed on the surfaces of planetary bodies, including the Earth, by high-speed impacts, are a basic landform on all the solid planets in the solar system. In prevailing models, a continuous sheet of ejected material forms during the excavation stage of cratering. Osinski and his team suggest that this stage is followed by a second major episode of ejecta emplacement during the final moments of crater formation – something that has not been taken into account in any previous models of crater formation. This second episode takes the form of flows of material molten by the impact event, which originates from deeper below the surface, potentially offering a unique window into planetary interiors. A more thorough understanding of the composition of planetary interiors reveals important insights into the history of how our solar system formed.

“It is rewarding to see that our international collaborations within the NASA Lunar Science Institute continue to make an impact on current theories and challenge fundamental principles in the field of lunar science,” said NLSI Director Yvonne Pendleton.


A. An image provided by the global mosaic of THEMIS daytime TIR imagery of a 18 km diameter crater within a 42 km diameter crater slowing a DLE morphology (NASA/JPL/ASU). Relative thermal inertias, as interpreted from the pre-dawn temperature differences with respect to this crater, suggest that the outer ejecta lobe is coarser-grained than the inner one, which is consistent with observations of the DLE Ries structure. B. In addition, the two ejecta layers are compositionally distinct (as observed in this decorrelation stretched THEMIS TIR 8-7-5 radiance composite (NASA/JPL/ASU): the outer ejecta faces (orange) has a more “basaltic” composition, while the inner ejecta (blue) layer has a more “ultramafic” composition (consists predominately of clinopyroxene and olivine [~70%]; see (Rogers et al., 2005)]). This ejecta blanket configuration is consistent with the “basaltic” materials originating from the near-subsurface and the “ultramafic unit” from a deeper unit underlying the “basaltic unit”. This stratigraphy is also consistent with the regional non-crater exposed stratigraphy in this area (Rogers et al., 2005). Credit: Osinski et al.

This research primarily was supported by the Industrial Research Chair in Planetary Geology held by Osinski and funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), MacDonald, Dettwiler and Associates and the Canadian Space Agency (CSA).

Osinski recently established the Canadian Lunar Research Network (CLRN), a network comprised of scientists, engineers and entrepreneurs from throughout Canada. In July 2008, CLRN became the first international affiliate partner of NASA’s Lunar Science Institute.

The NLSI is a virtual organization that enables collaborative, interdisciplinary research in support of NASA lunar science programs. The institute uses technology to bring scientists together around the world and comprises competitively selected U.S. teams and several international partners. NASA’s Science Mission Directorate and the Human Exploration Office in Washington, fund NLSI, which is managed by a central office at Ames.

For more information about the Canadian Lunar Research Network visit:

http://clrn.uwo.ca

Posted by: Soderman/NLSI Staff
Source: NLSI Team

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