Transcript Document

Seasonal and Daily Changes on Mars
•
•
•
•
•
•
•
Global and local dust storms;
Dust devils;
Eroded rock and dunes;
Polar Caps and their variation by season;
Layers within caps;
Other cold-climate features;
Cause of climate changes on Mars?
Global dust storms evolve in < 1 months, and last > 3 months
Dust Storms
Dust storm
Polar cap
Local dust storm on Mars
Dust storm
Africa
Dust storm from Sahara
Dust devil tracks – evidence for local winds and surface fines
Wind-scoured rocks are called “Yardangs”
The material eroded from rocks forms many dunes.
Show constant wind direction for long periods of time.
Wind erosion features on Mars
North Polar Cap
Water (H2O) ice
Low elevation
South Polar Cap
Carbon dioxide (CO2) ice
High elevation
Changing shape of the South Polar Cap due to seasons
Frost
Cap
Winter
Spring
Summer
MOLA data indicate that this eroding layer is about 10 cm thick
Polar Caps composed of hundreds of layers of ice and dust
Snow melt as possible mechanism for pit erosion
Polygonal ground as indicator of “freeze-thaw” process
So how do we get these
longer seasonal changes
on Mars?
The obliquity of Mars
may have varied from
almost 0 – 60 degrees
The precession may have
changed climate
dramatically in the past
on timescales of 25,000 –
175,000 years
Temperature change on Mars due to change in eccentricity
Present and past climates of Mars may be very different
Present – cold/dry
Past – cold and moist
Results from Viking Lander Gaschromatograph - Mass
spectrometer
Viking Biology Experiments
1. Labeled release experiment, looked for signs of
metabolism
2. Pyrolytic release experiment, looked for signs of
photosynthesis
3. Gas exchange experiment, looked for signs of
respiration
In 1996, possible “fossils” were found in a meteorite from Mars!
ALH 84001 originated as a slowly-cooled
igneous rock in the Martian crust, was
excavated by an impact, altered by fluids,
and finally sent to Earth by another
impact. The consensus among most
researchers is that these are not fossils
but”ludae naturae” (playthings of nature),
of inorganic origin.
More “pseudofossils” from Martian meteorite ALH 84001
Carbonates in Martian meteorite ALH 84001 formed by shock
Carbonate globules in Martian meteorite ALH 84001 are of inorganic origin