[meteorite-list] Recent Activity on Mars: Fire and Ice

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Feb 1 21:18:02 2005
Message-ID: <200502020217.SAA10728_at_zagami.jpl.nasa.gov>

http://www.psrd.hawaii.edu/Jan05/MarsRecently.html

Recent Activity on Mars: Fire and Ice
Planetary Science Research Discoveries
January 31, 2005

--- New images from Mars Express show evidence of recent volcanic and
glacial activity on Mars, consistent with what we know from Martian
meteorites and previous evaluations of the planet's internal heat
production and climate.

Written by Linda M. V. Martel
Hawai'i Institute of Geophysics and Planetology

Scientists combined the time-honored method of counting craters to
estimate the age of planetary surfaces with brand new high-resolution,
stereo images of Mars to reassess the planet's recent volcanic and
glacial activity. Gerhard Neukum (Freie Universit?t, Berlin, Germany)
and colleagues from Germany, United States, Russia, and the United
Kingdom studied calderas on five major
volcanoes and the shield of Olympus Mons with the High Resolution Stereo
Camera (HRSC) on the European Space Agency's Mars Express Spacecraft to
try to determine the duration of geologic activity more precisely than
had ever been done before. Their work confirms that the Tharsis and
Elysium regions were volcanically active over billions of years, that
caldera eruptions were episodic but were especially numerous 100 to 200
million years ago, and that the most recent lava flows on Mars may be as
young as two million years. Their findings are consistent with previous
studies of Mars Global Surveyor data as well as Martian shergottite
meteorites that suggest intermittent magmatism from 165 to about 500
million years ago. Neukum and coauthors also report the most recent
phase of glacial activity on Olympus Mons was within the past four
million years. So recent are these events in geologic time that the
researchers speculate high-altitude, insulted ice deposits may be
present on Olympus Mons even now and that volcanoes might still be active.

Reference:

    * Neukum, G., Jaumann, R., Hoffmann, H., Hauber, E., Head J. W.,
      Basilevsky, A. T., Ivanov, B. A., Werner, S. C., van Gasselt, S.,
      Murray, J. B., McCord, T., and the HRSC Co-investigator team
      (2004) Recent and episodic volcanic and glacial activity on Mars
      revealed by the High Resolution Stereo Camera. Nature, v. 432, p.
      971-979.

------------------------------------------------------------------------

New Ages

The High-Resolution Stereo Camera (HRSC) co-investigator team targeted
the summit calderas of five major shield volcanoes and the flanks of
Olympus Mons, known sites of relatively recent volcanic activity. They
defined specific terrain areas for counting craters using the 10
meters/pixel resolution images and the Super Resolution Channel's 2.5
meters/pixel resolution data along with nested Mars Orbiter Camera (MOC)
images. Previous age determinations using the crater counting technique
have been limited by poorer resolution or by the small areas imaged. For
a short explanation of the crater counting technique visit the Planetary
Science Institute web page
<http://www.psi.edu/projects/mgs/cratering.html>.

[graphic]
crater size frequency distribution curve Crater size-frequency
distribution for the caldera on Arsia Mons. Frequencies of craters per
unit area were counted on the caldera floor and plotted against crater
diameters to derive the absolute age of the surface at 130 million years
old. Similar log-log plots were constructed for each summit caldera.

The HRSC team used the unified cratering chronology model published in
2001 by Neukum and colleagues Boris Ivanov (Russian Academy of Sciences,
Moscow) and William Hartmann (Planetary Science Institute, Tucson,
Arizona) that concluded craters on the Moon and Mars were created by the
same family of projectiles and that the lunar cratering chronology could
be transferred to Mars. The ages derived from the Martian crater counts
are limited in accuracy, however. The main uncertainty is the
statistical error arising from the number of craters counted (the error
increases as age, hence the number of craters, decreases.) There is also
uncertainty in the underlying impact flux model used for Mars relative
to the lunar value. In the team's study, errors are approximately 20% to
30% for derived absolute ages younger than 3 billion years and 100 to
200 million years for ages older than 3 billion years.

The images below show the five volcanic calderas examined in this study:
Hecates Tholus, Albor Tholus, Arsia Mons, Ascraeus Mons, and Olympus
Mons. In the left column are HRSC images of the five volcanic caldera
complexes. They should appear as depressions (sun shining from the lower
left corner). North is to the top of each image. In the right column are
the crater-counting areas defined by Neukum and colleagues, which are
labeled with their derived absolute ages.

Click for more information
<http://www.esa.int/export/SPECIALS/Mars_Express/SEMTXD2PGQD_0.html>

Neukum and coauthors mapped five different caldera collapse events on
Hectates Tholus with floors ranging in age from approximately 2 billion
years old to about 100 milliion years old. [Additional images from ESA
Mars Express
<http://www.esa.int/export/SPECIALS/Mars_Express/SEMTXD2PGQD_0.html>.]

Albor Tholus

The four caldera floors mapped on Albor Tholus range in age from
approximately 2.2 billion years old to about 500 million years old.

Arsia Mons

The summit of Arsia Mons is dominated by a single huge caldera. The
floor is dated at about 130 millions years old.

Ascraeus Mons

A large central caldera floor, dated at approximately 100 million years
old, cuts adjacent caldera floors of various ages.

Click for more information
<http://www.esa.int/export/SPECIALS/Mars_Express/SEM9BA1PGQD_1.html>

Olympus Mons is unusual by comparison with the other caldera complexes
because the five caldera segments have ages clustering around 100 to 200
million years old. In the simplest stratigraphic sense, the top-most
features are the youngest. However, the absolute ages assigned to the
floors of the five calderas on Olympus Mons seem to defy this and some
would argue against the validity of the assigned ages. Nevertheless, the
researchers explain that since the different ages are very similar
within the error limits of ? 50 million years, we must keep in mind that
the formation of all the calderas on Olympus Mons could have happened in
a short time span around 150 million years ago. [Additional information
and high resolution images from ESA Mars Express
<http://www.esa.int/export/SPECIALS/Mars_Express/SEM9BA1PGQD_1.html>.]

The image below shows an area of the western scarp of Olympus Mons where
sparsely cratered lava flows were reexamined with the HRSC and MOC images.

counting areas on Olympus Mons shield
<http://www.msss.com/moc_gallery/e07_e12/images/E10/E1000828.html>

Surfaces were dated using the crater size-frequency technique. The
shaded areas show crater counting areas. Ages of the lava flows range
from 115 million years to about two million years in the area where HRSC
and MOC data were combined. [Additional information and high resolution
MOC image
<http://www.msss.com/moc_gallery/e07_e12/images/E10/E1000828.html>.]

------------------------------------------------------------------------

Internal heat and magma supply

The calderas on five major volcanoes have undergone repeated activity as
shown by the different ages of caldera floors created by different
collapse events. Based on the crater size-frequency measurements by the
HRSC team in these multiple calderas, magma reservoirs were forming,
solidifying, and reforming on time scales of about 20 million years. The
very long activity of Martian volcanoes implies correspondingly long
lifetimes of hot spots in the planet's interior. These findings by
Neukum and coauthors are in agreement with theoretical analyses and
geological studies that suggest subsurface magma reservoirs must cool
and solidify between caldera collapse events. Magma supply to the major
shield volcanoes on Mars was episodic rather than continuous. What's
more, the youngest volcanic surfaces in the study areas are so
geologically young (about two million years) that volcanoes must have
been active within the last 2% to 4% of Martian history.

The HRSC team's conclusions for recent volcanic activity and an
internally active Mars are completely consistent with what we know from
other studies:

    * Martian meteorites. Most of the Martian meteorites formed in lava
      flows or shallow magma bodies during Amazonian
      times (see histogram below.)
      Shergottites are the most abundant type. All the basaltic
      shergottites have crystallization ages less than 500 million
      years, with eight of the rocks in the range of 165 to 180 million
      years. Although these individual rocks are far from a
      representative sampling of Martian lava flows, they do suggest
      intermittent magmatism during the past 500 million years and there
      is no reason to think there couldn't be even younger volcanic
      deposits.

    * Previous interpretations of Mars Global Surveyor (MGS) camera, and
      Mars Orbiter Laser Altimeter (MOLA) data. Results from 2001
      studies suggested sporadic volcanic activity lasted 100 million
      years or longer with estimated ages of 3 to 10 million years old
      for the youngest surfaces. Based on these young surface ages,
      studies of eruption rates, and the episodic eruption style, many
      researchers, including Susan Sakimoto (NASA Goddard Earth Science
      and Technology Center) concluded that the potential for volcanic
      eruptions occurring during the next several tens of millions of
      years on Mars was not out of the question. [See Leonard David's
      space.com article: Mars Volcanoes Still Alive After All These
      Years?
      <http://www.space.com/scienceastronomy/solarsystem/mars_volcano_011113.html>.]


    * Current interpretations of the Mars Odyssey Gamma Ray Spectrometer
      data and geophysical modeling. Using the crustal average values
      for potassium and thorium from Mars Odyssey GRS data, the GRS team
      has calculated that half of the planet's potassium and thorium is
      in the crust. That leaves half in the mantle. [Mars Odyssey GRS
      results are about to be submitted for publication, but see Taylor,
      G. J. et al. (2003) Igneous and aqueous processes on Mars:
      Evidence from measurements of K and Th by the Mars Odyssey Gamma
      Ray Spectrometer. Sixth International Conference on Mars, 3207
      ] Steve Hauck and Roger
      Phillips (Washington University, St. Louis) and Walter Kiefer
      (Lunar and Planetary Institute, Houston) calculated that if
      approximately half of the radioactive elements such as potassium,
      thorium, and uranium were left in the mantle, there would be
      enough heat source for a small amount of volcanic activity today
      on Mars.

------------------------------------------------------------------------

The Time Scale is Geologic not Human

If the volcanoes on the Red Planet are potentially still active, then
eruptions could occur. But when? Would any of the active ESA and NASA
Mars missions record the event? The most reasonable forecast for any
possible future volcanic activity is in another couple to tens of
millions of years...well into the future by human standards. To put it
into perspective, the lava flows on Mars are akin to those that erupt
from volcanoes in Hawaii. But an eruption on Oahu (where the youngest
volcanic rocks are only about 100,000 to 500,000 years old) is more
likely than on Mars. Is there a chance of seeing a volcanic eruption on
Oahu in our lifetime? A geologist will tell you it is possible, but the
odds are actually slim. The same may be said for Mars.

------------------------------------------------------------------------

Glaciers on the Shield of Olympus Mons

Glacial deposits at the base of the Olympus Mons scarp look like rock
glaciers or debris-covered glaciers on Earth and are interpreted as
evidence for repeated phases of activity. Rock glaciers are typically
covered by rocks and boulders and often have ridges, furrows, and lobes
on the surface. [See Milkovich and Head (2003) Olympus Mons Fan Shaped
Deposit Morphology: Evidence for Debris Glaciers. Sixth International
Conference on Mars, 3149.

Neukum and coauthors found that the crater size-frequency distributions
for these deposits ranged from 130 to 280 million years for the major
lobes, 20 to 60 million years for some subareas, and four million years
for the youngest surfaces. Snow/ice deposition on the Olympus Mons
shield at elevations higher than 7000 meters may have led to episodes of
glacial activity at this height. The data suggest that water ice
protected by an insulating layer of dust may now exist at high altitudes
at the edge of the Olympus Mons shield. Accumulations of water ice in
non-polar regions are particularly hot topics of research because of
their implications for hydrothermal activity and the strategy for
searching for life on Mars.

Olympus Mons scarp
This perspective view of the western scarp of Olympus Mons shows steep
gullied slopes, channels, and glacier-like flows.

------------------------------------------------------------------------

More Mars Express Results

The first Mars Express Science Conference <http://www.congrex.nl/05C05/>
will be held February 21-25, 2005 in Noordwijk, The Netherlands. The
scientific community involved in Mars Express will review the progress
toward understanding Mars and put the results in the broader context of
the latest scientific interpretations derived from current NASA
missions: Mars Global Surveyor, Mars Odyssey, and Mars Exploration Rover.

------------------------------------------------------------------------

ADDITIONAL RESOURCES LINKS OPEN IN A NEW WINDOW.

    * Borg, L. E., Nyquist, L. E., Weissman, H., Shih, C.-Y., and Reese,
      Y. (2003) The age of Dar al Gani 476 and the differentiation
      history of the Martian meteorites inferred from their radiogenic
      isotopic systematics. Geochim. Cosmochim. Acta, v. 67, p. 3519-3536.

    * David, L. (2001) Mars Volcanoes: Still Alive After All These
      Years? space.com
      http://www.space.com/scienceastronomy/solarsystem/mars_volcano_011113.html.

    * European Space Agency's Mars Express Mission homepage
      <http://www.esa.int/SPECIALS/Mars_Express/index.html> and image
      browser <http://www.esa.int/SPECIALS/Mars_Express/SEMVZF77ESD_0.html>.

    * Hartmann, W. K. and Neukum, G. (2001) Cratering chronology and the
      evolution of Mars. Space Science Reviews, v. 96, p. 165-194.

    * Hauck, S. A. and Phillips, R. J. (2002) Thermal and crustal
      evolution of Mars. Journal of Geophysical Research, v. 107, doi
      10.1029/2001JE0011801.

    * Introduction to Cratering Studies and the Crater Counting
      Technique <http://www.psi.edu/projects/mgs/cratering.html> from
      the Planetary Science Institute, Tucson, Arizona.

    * Kiefer, W. S. (2003) Melting in the Martian mantle: Shergottite
      formation and implications for present-day mantle convection on
      Mars. Meteoritics and Planetary Science, v. 38, p. 1815-1832.

    * Milkovich, S M. and Head III, J. W. (2003) Olympus Mons Fan Shaped
      Deposit Morphology: Evidence for Debris Glaciers. Sixth
      International Conference on Mars, 3149 <SixthMarsConf_MSM_JWH.pdf>
      (pdf file).

    * Neukum, G., Jaumann, R., Hoffmann, H., Hauber, E., Head J. W.,
      Basilevsky, A. T., Ivanov, B. A., Werner, S. C., van Gasselt, S.,
      Murray, J. B., McCord, T., and the HRSC Co-investigator team.
      (2004) Recent and episodic volcanic and glacial activity on Mars
      revealed by the High Resolution Stereo Camera. Nature, v. 432, p.
      971-979.

    * Neukum, G., Ivanov, B. A., and Hartmann, W. K. (2001) Cratering
      records in the inner solar system in relation to the lunar
      reference system. Space Science Reviews, v. 96, p. 55-86.

    * Nyquist, L. E. et al, (2001) Ages and geologic histories of
      Martian meteorites. Space Science Reviews, v. 96, p. 105-164.

    * Mars Odyssey GRS results are about to be submitted for
      publication, but see Taylor, G. J. et al. (2003) Igneous and
      aqueous processes on Mars: Evidence from measurements of K and Th
      by the Mars Odyssey Gamma Ray Spectrometer. Sixth International
      Conference on Mars, 3207 <SixthMarsConf_TaylorGRS.pdf> (pdf file).
Received on Tue 01 Feb 2005 09:17:48 PM PST