Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p51b1434l&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P51B-1434
Mathematics
Logic
[5410] Planetary Sciences: Solid Surface Planets / Composition, [5480] Planetary Sciences: Solid Surface Planets / Volcanism, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
A long-standing problem in the study of Mars has been the incompatibility between 1) geochemically-based expectations for low near-surface water abundance; and 2) the large water volumes required of aqueous interpretations of the outflow channels. On the basis of the compositions of SNC meteorites and the current Martian atmosphere, the early water content of Mars has been estimated by several groups to be equivalent to a global layer of ~6 to 200 m thickness, only a proportion of which would have been outgassed to the near-surface environment. In contrast, previous estimates of the minimum near-surface water volume required if the Martian outflow channels formed through aqueous mechanisms are equivalent to a global water layer of 300-500 m thickness, assuming unrealistic sediment loads of 40% and an absence of infiltration or evaporation during flow, and ignoring volumes such as those required of hypothesized cryospheric seals. Under more realistic outflow scenarios, required volumes are likely to be equivalent to an Earth-like global layer of at least several kilometers thickness, even assuming the past operation of a vigorous hydrological cycle. Some workers have suggested that disagreement between geochemical and geomorphological estimates of near-surface water volumes on Mars might be resolved if the amount of water outgassed by the planet was greater than expected, or if especially large volumes of water were contributed to the surface by impacts of volatile-rich bodies late in the heavy bombardment of Mars. However, resolution is instead likely to follow from changes in perspectives regarding outflow channel origins. Though most workers currently accept aqueous interpretations, recent work has indicated that the outflow channels of Mars are very likely to be the products of volcanic processes involving incision by low-viscosity mafic lavas. Volcanic interpretations are consistent with numerous considerations, including the absence of channel deposits of clear fluvial or diluvial origin, the widespread volcanic mantling of channels, the presence of large volcanic plains at terminal basins, and the availability of lunar and Venusian analogs for development of large channel systems through eruption of low-viscosity lava. Importantly, a volcanic origin for the Martian outflow channels removes the basis for past hypotheses involving aqueous outflow environments and associated oceans and aquifers, bringing outflow channel origins into conformity with previous geochemical estimates for low near-surface water volumes, and with independent mineralogical evidence suggesting predominantly cold and dry conditions during the Hesperian and Amazonian. A volcanic origin for the Martian outflow channels dramatically narrows the possible range of environments once supportive of Hesperian or Amazonian life, and might reduce the broader likelihood of past life on Mars by diminishing geomorphological justifications for the past existence of unexpectedly immense near-surface water reservoirs.
No associations
LandOfFree
Inconsistencies in Estimates of Near-Surface Water Abundance are Resolved by the Volcanic Origin of Martian Outflow Channels does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Inconsistencies in Estimates of Near-Surface Water Abundance are Resolved by the Volcanic Origin of Martian Outflow Channels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inconsistencies in Estimates of Near-Surface Water Abundance are Resolved by the Volcanic Origin of Martian Outflow Channels will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1497713