A paleo-ocean detected on Mars
The fact that Mars had had a huge ocean is now in
2015 recognized more and more by mainstream science. This hypothesis of a “paleo-ocean”
(and the first geological and chemical data supporting it) was first proposed
in 1987 by physicist and plasma expert John E. Brandenburg, at a MECA
symposium (See the link below to this original abstract).
Search the web for articles on “Mars’ paleo-ocean.”
Below is the Wikipedia one, still cautious and presenting it as an hypothesis,
despite the fact that scientific proofs from diverse fields abound. With the
discovery of this paleo-ocean come definite indices that Mars in its early
life (from 3.8 billion years ago to at least 1 or 1.5 billion years ago), had an
atmosphere and streams, life forms, plentiful vegetation, and moreover a
developed civilization.
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Wikipedia article: Mars paleo-ocean hypothesis
http://en.wikipedia.org/wiki/Mars_ocean_hypothesis
An
artist's impression of ancient Mars and its oceans based on geological data
The Mars ocean hypothesis states that nearly a third of the surface of
Mars was covered by an ocean of liquid water early in the
planet’s geologic history.[2][3] This primordial ocean, dubbed
Paleo-Ocean[1] and Oceanus Borealis,[4] would have filled the Vastitas Borealis basin in the northern
hemisphere, a region which lies 4–5 km (2.5–3 miles) below the mean
planetary elevation, at a time period of approximately 3.8 billion years ago.
Evidence for this ocean includes geographic features resembling ancient
shorelines, and the chemical properties of the Martian soil and atmosphere.
Early Mars would have required a denser atmosphere and warmer climate to allow
liquid water to remain at the surface.[5]
The blue
region of low topography in the Martian northern hemisphere is hypothesized
to
be the site of a primordial ocean of liquid water.[1]
History of observational evidence
Features shown by the Viking orbiters in 1976, revealed two possible ancient shorelines near
the pole, Arabia and Deuteronilus, each thousands of kilometers long.[6] Several physical features in the
present geography of Mars suggest the past existence of a primordial ocean.
Networks of gullies that merge into larger channels imply erosion by a liquid
agent, and resemble ancient riverbeds on Earth. Enormous channels, 25 km
wide and several hundred meters deep, appear to direct flow from underground
aquifers in the Southern uplands into the Northern plains.[5] Much of the northern hemisphere
of Mars is located at a significantly lower elevation than the rest of the
planet (the Martian
dichotomy), and is unusually flat.
These observations led a number of researchers to
look for remnants of more ancient coastlines and further raised the possibility
that such an ocean once existed.[7] In
1987, John E. Brandenburg published the hypothesis of a primordial Mars
ocean he dubbed Paleo-Ocean.[1] The ocean hypothesis is important because the
existence of large bodies of liquid water in the past would have had a
significant impact on ancient Martian climate, habitability potential and
implications for the search for evidence of past life on Mars.
[See * Brandenburg, John E.
(1987), "The
Paleo-Ocean of Mars", MECA Symposium on Mars: Evolution of
its Climate and Atmosphere, Lunar and Planetary Institute, pp. 20–22, retrieved 19 February 2014.)
* Brandenburg,
John E. (2015). Death on Mars: The
Discovery of a Planetary Nuclear Massacre. Adventures Unlimited Press.]
Beginning in 1998, scientists Michael Malin and Kenneth Edgett set out
to investigate with higher resolution cameras on board the Mars Global Surveyor with a resolution five to ten times better than
Viking, in places that would test shorelines proposed by others in the
scientific literature.[7] Their analysis were inconclusive
at best, and reported that the shoreline varies in elevation by several
kilometers, rising and falling from one peak to the next for thousands of
miles.[8] These trends casted doubt on
whether the features truly marked a long-gone sea coast and, have been taken as
an argument against the Martian shoreline (and ocean) hypothesis.
The Mars Orbiter Laser Altimeter (MOLA), which accurately determined in
1999 the altitude of all parts of Mars, found that the watershed for an ocean
on Mars would cover three-quarters of
the planet.[9] The unique distribution of
crater types below 2400 m elevation in the Vastitas Borealis was studied in
2005. The researchers suggest that erosion involved significant amounts of sublimation, and an ancient ocean at that location would have encompassed a volume of 6 x 107
km3.[10]
Scientists Taylor Perron and Michael Manga, proposed in 2007 a geophysical
model that, after adjustment for true polar wander caused by mass
redistributions from volcanism, the Martian paleo-shorelines first proposed in
1987 by John E. Brandenburg,[1] meet this criterion.[11] The model indicates that these
undulating Martian shorelines "can be explained by the movement of Mars'
spin axis". Because spinning objects bulge at their equator, the polar
wander could have caused shoreline elevation shifts similar to those observed
on Mars.[6][12][13] Their model does not attempt to
explain what caused Mars' rotation axis to move relative to the crust.
Research published in 2009 shows a much higher density of stream
channels than formerly believed. Regions on
Mars with the most valleys are comparable to what is found on the Earth. In the
research, the team developed a computer program to identify valleys by
searching for U-shaped structures in topographical data.[14] The large amount of valley
networks strongly supports rain on the planet in the past. The global pattern of the Martian valleys could be explained with a big
northern ocean. A large ocean in the northern hemisphere would explain why
there is a southern limit to valley networks; the southernmost regions of Mars,
farthest from the water reservoir, would get little rainfall and would develop
no valleys. In a similar fashion the lack of rainfall would explain why Martian
valleys become shallower from north to south.[15]
A 2010 study of deltas on Mars
revealed that seventeen of them are found at the altitude of a proposed
shoreline for a Martian ocean.[16] This is what would be expected
if the deltas were all next to a large body of water.[17]
Research published in 2012 using
data from MARSIS, a radar on board the Mars Express orbiter, supports the
hypothesis of an extinct large, northern ocean. The instrument revealed a
dielectric constant of the surface that is similar to with low-density sedimentary deposits, massive deposits of ground-ice,
or a combination of the two. The measurements were not like those of a lava-rich
surface.[18]
Theoretical issues
Primordial Martian climate
The existence of liquid water on
the surface of Mars requires both a warmer and thicker atmosphere [than presently]. Atmospheric pressure on the present day Martian surface only exceeds that of
the "triple point of water"(6.11 hPa) in the
lowest elevations; at higher elevations water can exist only in solid or vapor
form (assuming pure water). Annual mean
temperatures at the surface are currently less than 210 K, significantly less
than what is needed to sustain liquid water. However, early in its history Mars
may have had conditions more conducive to retaining liquid water at the
surface.
Early Mars had a carbon dioxide
atmosphere similar in thickness to present-day Earth (1000 hPa).[19] Despite a weak early sun, the greenhouse effects from a thick carbon
dioxide atmosphere, if bolstered with small amounts of methane[20] or insulating effects of carbon
dioxide ice clouds,[21] would have been sufficient to
warm the mean surface temperature to a value above the freezing point of water.
The atmosphere has since been reduced by sequestration
in the ground in the form of carbonates through weathering,[19] as well as loss to space
through sputtering (an interaction with the solar
wind due to the lack of a strong Martian magnetosphere).[22][23]
The obliquity (axial tilt) of Mars varies considerably on
geologic timescales, and has a strong impact on planetary climate conditions.[24]
Chemistry
Consideration of chemistry can
yield additional insight into the properties of Oceanus Borealis. With a Martian atmosphere of predominantly carbon
dioxide, one might expect to find extensive evidence of carbonate minerals
on the surface as remnants from oceanic sedimentation. An abundance of
carbonates has yet to be detected by the Mars space missions. However, if the
early oceans were acidic, carbonates would not be able to form.[25] The positive correlation of
phosphorus, sulfur, and chlorine in the soil at two landing sites suggest
mixing in a large acidic reservoir.[26] Hematite deposits detected by
TES have also been argued as evidence of past liquid water.[27]
Analysis of molecular hydrogen to deuterium ratios in the upper Mars
atmosphere from the NASA Far
Ultraviolet Spectroscopic Explorer spacecraft suggests an abundant
water supply on primordial Mars.[28]
Fate of the ocean
Given the proposal of a vast
primordial ocean on Mars, the fate of the water requires explanation. As the
Martian climate cooled, the surface of the ocean would have frozen. One
hypothesis states that part of the ocean remains in a frozen state buried
beneath a thin layer of rock, debris, and dust on the flat northern plain Vastitas Borealis.[29] The water could have also been
absorbed into the subsurface cryosphere[3] or been lost to the atmosphere
(by sublimation) and eventually to space through atmospheric sputtering.[22]
Alternate explanations
The existence of a primordial
Martian ocean remains controversial among scientists. The Mars
Reconnaissance Orbiter's High
Resolution Imaging Science Experiment (HiRISE) has discovered large
boulders on the site of the ancient seabed, which should contain only fine
sediment.[30] However, the boulders could
have been dropped by icebergs, a
process common on Earth.[31][32] The interpretations of some
features as ancient shorelines has been challenged.[33]
Alternate theories for the
creation of surface gullies and channels include wind erosion,[34]
liquid carbon dioxide,[5]
and liquid methane.[27]
Confirmation or refutation of the
Mars ocean hypothesis awaits additional observational evidence from future Mars
missions.
References
1.
Brandenburg, John E.
(1987), "The
Paleo-Ocean of Mars", MECA Symposium on Mars: Evolution of
its Climate and Atmosphere, Lunar and Planetary Institute, pp. 20–22,
retrieved 19 February 2014. |1987meca.symp...20B. Find
it at: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1987meca.symp...20B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf See also:
Brandenburg, John E. (2015). Death on Mars: The
Discovery of a Planetary Nuclear Massacre. Adventures
Unlimited Press.]
2.
Cabrol, N. and E. Grin (eds.). 2010. Lakes on
Mars. Elsevier. NY
3. Clifford, S. M.
and T. J. Parker, 2001: The Evolution of the Martian
Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current
State of the Northern Plains, Icarus 154, 40-79.
4. Baker, V. R.,
R. G. Strom, V. C. Gulick, J. S. Kargel, G. Komatsu and V. S. Kale, 1991:
Ancient oceans, ice sheets and the hydrological cycle on Mars, Nature, 352,
589-594.
5. Read, Peter L.
and S. R. Lewis, “The Martian Climate Revisited: Atmosphere and Environment of
a Desert Planet”, Praxis, Chichester, UK, 2004.
6. "Mars Probably Once Had A Huge
Ocean". University of California - Berkeley (Science
Daily). 13 June 2007. Retrieved 2014-02-19.
7. "Mars Ocean Hypothesis Hits the
Shore". Astrobiology Magazine. 26 January 2001.
Retrieved 19 February 2004.
8. Malin, M. C.,
and Edgett, K. S., 1999. Oceans or Seas in the Martian Northern Lowlands:
High Resolution Imaging Tests of Proposed Coastlines, Geophys. Res.
Letters, V. 26, No. 19, p. 3049—3052
9. Smith, D. et
al. 1999. Science: 284.1495
10. Boyce, J. M.; Mouginis,
P.; Garbeil, H. (2005). "Ancient oceans in the northern
lowlands of Mars: Evidence from impact crater depth/diameter
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of Geophysical Research (American
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12. Perron, J. Taylor;
Jerry X. Mitrovica, Michael Manga, Isamu Matsuyama and Mark A. Richards (14
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13. Dunham, Will (13 June
2007). "Evidence seen backing ancient
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14. "Martian North Once Covered by
Ocean". Astrobiology Magazine. 26 November 2009.
Retrieved 19 February 2014.
15. "New Map Bolsters Case for
Ancient Ocean on Mars". Space.com. 23 November 2009.
Retrieved 2014-02-19.
16. DiAchille, G
and B. Hynek. 2010. Ancient ocean on Mars supported by global distribution of
deltas and valleys. nat. Geosci. 3, P. 459-463, doi:10.1038/ngeo891
17. DiBiasse, A.
Limaye, J. Scheingross, W. Fischer, and M. Lamb. 2013. Deltic deposits at
Aeolis Dorsa: Sedimentary evidence for a standing body of water on the northern
plains of Mars. Journal of Geophysical Research Planets 118, 1285-1302
18. Mouginot, J.,
A. Pommerol, P. Beck, W. Kofman, S. Clifford. 2012. Dielectric map of the
Martian northern hemisphere and the nature of plain filling materials. Geophysical
Research Letters, Vol. 39, L02202, doi:10.1029/2011GL050286
19. Carr, Michael
H., 1999: Retention of an atmosphere on early Mars, Journal of Geophysical
Research, 104, 21897-21909.
20. Squyres, Steven
W. and James F. Kasting, 1994: Early Mars: How warm and how wet?, Science,
265, 744-749.
21. Forget, F. and
R. T. Pierrehumbert, 1997: Warming Early Mars with Carbon Dioxide Clouds That
Scatter Infrared Radiation, Science, 278, 1273-1276.
22. Kass, D. M. and
Y. L. Yung, 1995: Loss of atmosphere from Mars due to solar wind-induced
sputtering, Science, 268, 697-699.
23. Carr, M and J.
Head III. 2003. Oceans on Mars: An assessment of the observational evidence and
possible fate. Journal of Geophysical Research: 108. 5042.
24. Abe, Yutaka,
Atsushi Numaguti, Goro Komatsu, and Yoshihide Kobayashi, 2005: Four climate
regimes on a land planet with wet surface: Effects of obliquity change and
implications for ancient Mars, Icarus, Volume 178, Pages 27-39.
25. Fairen, A.G.,
D. Fernadez-Remolar, J. M. Dohm, V.R. Baker, and R. Amils, 2004: Inhibition of
carbonate synthesis in acidic oceans on early Mars, Nature, 431,
423-426.
26. Greenwood,
James P. and Ruth E. Blake, 2006: Evidence for an acidic ocean on Mars from
phosphorus geochemistry of Martian soils and rocks, Geology, 34,
953-956.
27. Tang, Y., Q.
Chen and Y. Huang, 2006: Early Mars may have had a methanol ocean, Icarus,
181, 88-92.
28. Krasnopolsky,
Vladimir A., and Paul D. Feldman, 2001: Detection of Molecular Hydrogen in the
Atmosphere of Mars, Science, 294, 1914-1917.
29. Janhunen, P.,
2002: Are the northern plains of Mars a frozen ocean?, Journal of
Geophysical Research, 107, 5103.
30. Kerr, Richard
A., 2007: Is Mars Looking Drier and Drier for Longer and Longer?, Science,
317, 1673.
31. Fairén, A. G.; Davila, A. F.; Lim, D.; McKay, C. (2010). "Icebergs on Early Mars".
Astrobiology Science Conference.
Retrieved 2010-10-02.
32. Chol, Charles Q.
(2010-10-01). "New Evidence Suggests Icebergs
in Frigid Oceans on Ancient Mars". Space.Com
web site. Retrieved 2010-10-02.
33. Carr, M. H. and
J.W. Head, 2002: Oceans on Mars: An assessment of the observational evidence
and possible fate, Journal of Geophysical Research, 108.
34. Leovy, C.B.,
1999: Wind and climate on Mars, Science, 284, 1891a.
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See also: John Brandenburg original 1987 presentation
at MECA symposium.
1987meca.symp...20B
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1987meca.symp...20B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf