Mars' Climate in Flux: Mid-Latitude Glaciers (Forwarded)

Geological Society of America
Boulder, Colorado

Contact:
Ann Cairns, Director–Communications and Marketing
(303) 357-1056, fax 303-357-1074

FOR IMMEDIATE RELEASE: 14 October 2005

GSA Release No. 05-37

Mars' Climate in Flux: Mid-Latitude Glaciers

New high-resolution images of mid-latitude Mars are revealing
glacier-formed landscapes far from the Martian poles, says a leading
Mars researcher.

Conspicuous trains of debris in valleys, arcs of debris on steep slopes
and other features far from the polar ice caps bear striking
similarities to glacial landscapes of Earth, says Brown University's
James Head III. When combined with the latest climate models and orbital
calculation for Mars, the geological features make a compelling case for
Mars having ongoing climate shifts that allow ice to leave the poles and
accumulate at lower latitudes.

"The exciting thing is a real convergence of these things," said Head,
who will present the latest Mars climate discoveries on Sunday, 16
October, at the Annual Meeting of the Geological Society of America in
Salt Lake City (specific time and location provided below).

"For decades people have been saying that deposits at mid and equatorial
latitudes look like they are ice-created," said Head. But without better
images, elevation data and some way of explaining it, ice outside of
Mars' polar regions was a hard sell.

Now high-resolution images from the Mars Odyssey spacecraft's Thermal
Emission Imaging System combined with images from the Mars Global
Surveyor spacecraft's Mars Orbiter Camera and Mars Orbiter Laser
Altimeter can be compared directly with glacier features in mountain and
polar regions of Earth. The likenesses are hard to ignore.

For instance, consider what Head calls "lineated valley fill". These are
lines of debris on valley floors that run downhill and parallel to the
valley walls, as if they mark some sort of past flow. The same sorts of
lines of debris are seen in aerial images of Earth glaciers. The
difference is that on Mars the water ice sublimes away (goes directly
from solid ice to gas, without any liquid phase between) and leaves the
debris lines intact. On Earth the lines of debris are usually washed
away as a glacier melts.

The lines of debris on Mars continue down valleys and converges with
other lines of debris -- again, just like what's seen on Earth where
glaciers converge.

"There's so much topography and the debris is so thick (on Mars) that
it's possible some of the ice might still be there," said Head. The
evidence for present day ice includes unusually degraded recent impact
craters in these areas -- just what you'd expect to see if a lot of the
material ejected from the impact was ice that quickly sublimed away.

Another peculiarly glacier-like feature seen in Martian mid-latitudes
are concentric arcs of debris breaking away from steep mountain alcoves
-- just as they do at the heads of glaciers on Earth.

As for how ice could reach Mars lower latitudes, orbital calculations
indicate that Mars may slowly wobble on its spin axis far more than
Earth does (the Moon minimizes Earth's wobble). This means that as Mars'
axis tilted to the extremes -- up to 60 degrees from the plane of Mars'
orbit -- the Martian poles get a whole lot more sunshine in the
summertime than they do now. That extra sun would likely sublime water
from the polar ice caps, explains Head.

"When you do that you are mobilizing a lot of ice and redistributing it
to the equator," Head said. "The climate models are saying it's possible."

It's pure chance that we happen to be exploring Mars when its axis is at
a lesser, more Earth-like tilt. This has led to the false impression of
Mars being a place that's geologically and climatically dead. In fact,
says Head, Mars is turning out to be a place that is constantly changing.

WHEN AND WHERE

Lineated Valley Fill at the Dichotomy Boundary on Mars: Evidence for
Regional Mid-Latitude Glaciation
Sunday, 16 October, 3:15 p.m. MDT, Salt Palace Convention Center Room 257

View abstract:
http://gsa.confex.com/gsa/2005AM/fin...ract_94125.htm

CONTACT INFORMATION

During the Geological Society of America Annual Meeting, 16-19 October,
contact Ann Cairns at the GSA Newsroom, Salt Palace Convention Center,
for assistance and to arrange for interviews: +1-801-534-4770.

After the meeting contact:
James Head III
Department of Geological Sciences
Brown University, Providence, RI
Phone: +1-401-863-2526

IMAGE CAPTIONS:
[Figure 1:
http://www.geosociety.org/news/pr/05-37_Fig1.htm]
The fretted channel and lineated valleys of the central
Deuteronilus-Protonilus Mensae region.

a. A Viking Orbiter mosaic and map. Boxes show locations of images in
Fig. 2.
b. Color topographic map with each contour line showing
400-meter-elevation difference.
c. Map showing alcoves (narrow arrows) and broad flow trends of lineated
valley fill on the valley floor (wide arrows). From Mars Express High
Resolution Stereo Camera, THEMIS and MOC images.
d. Topographic profiles from north to south across the same region. From
MOLA locations shown in b).

[Figure 2:
http://www.geosociety.org/news/pr/05-37_Fig2.htm]
A closer look with at the alcoves and lineated valley fill seen in Fig
1. The locations of these THEMIS & higher resolution MOC images are
marked in Fig. 1a.

a. Four alcoves cutting into the plateau at the bottom of the picture,
each with a lobes flowing down and outwards into the adjacent lineated
valley fill. Note how these lobes merge trends of the lineated valley
fill on the valley floor tothte left.
b. East-facing alcoves with multiple concentric-ridged lobes extending
east and converging with the lineated valley fill on the valley floor.
c. An even closer look at the deformed ridges and pitting on the valley
floor of Fig. 2b.
d. The outflow of two ridged lobes from alcoves (bottom left and right)
as they join a major lineated vally fill of area C (upper right) near
the convergence with B (Fig. 1c). The left lobe is swept westward,
forming broad arcing folds while the right lobe is increasingly
compressed until it resembles a tight isoclinal fold. Both lobes
ultimately merge into the general lineated valley fill parallel to the
valley walls.
e. Detail of siedways lobe-like flows converging into the lineated
valley fill on the valley floor, where flows merge from areas A and D.
f. A major east-facing zone of multiple alcoves and converging lobe-like
flows in the more disatant reaches of the system, along the edge of the
northernmost large mesa (area G). Note the concentric-outward ridges
reaching out from the alcoves and their progressing compression, folding
and flattening as the ridges deform and become part of the lineated
valley fill on the valley floor.
g. The northern reaches of the lineated valley system. The lineated
valley fill splits in two (bottom right) and flows around a massif to
create a broad up-flow collar and a diffuse, down-flow wake.

Figure credits: Amanda Nahm, Brown University