Wintertime CO2 Frost Formation Could be the Mechanism behind H2O Ice Patches in the Martian Northern Hemisphere By Eric Beitia (Northern Arizona University, Flagstaff Arizona) Project leader Dr. Timothy N. Titus (United States Geological Survey, Flagstaff Arizona)

Temperature On Mars CO2 solidifies at ~ 150 K (-123º C) On Earth CO2 solidifies at 200 K (-73° C) On Mars H2O solidifies at ~ 200 K (-73º C) On Earth H2O solidifies at 273 K (0° C) Solar longitude (Ls) Identifies season of the planet Each month corresponds to 30 degrees Ls

THEMIS (Thermal Emission Imaging System) data 266E 70N NORTH IR image Temp = 190 K / 220 K NORTH Get rid of left crater (42E 69N) Visible image

The Hypothesis of Ice Patch Formation Autumn/Winter Winter Spring Mid-Spring Add layer of CO2 ice under everything Late spring Spring/Summer CO2 Snow CO2 Ice H2O Ice

Ice patches found ~8000 THEMIS images 24 Ice patches

THEMIS (Thermal Emission Imaging System) data 266E 70N 42E 69N NORTH NORTH IR image Temp = 190 K / 220 K (-83º C/-53º C) Ls = 54 (mid-spring) Earth time = May 2006, Mars year 28 IR image Temp = 168 K / 216 K (-105º C/-57º C) Ls = 61 (mid-spring) Earth time = June 2006, Mars year 28 NORTH NORTH Visible image Ls = 87 (end of spring) Earth time = August 2006 Mars year 28 Visible image Ls = 62 (mid-spring) Earth time = July 2004 Mars year 27

TES (Thermal Emission Spectrum) data NORTH NORTH 266E 70N Warm colors represent solid ice (CO2) Cool colors represent fine grain (CO2) snow 42E 69N Warm colors represent solid ice (CO2) Cool colors represent fine grain (CO2) snow

Ice patches found 24 Ice patches with cold spot activity 24 Ice patches showed annual repetitive behavior

Conclusions: We use THEMIS data to show 24 craters with ice patch activity Successfully found 24 ice patches that have had cold spot activity earlier in the year with TES data Ice Patch activity repeats yearly for all 24 craters Future work would be to find many more craters with similar characteristics

The end!!!

Autumn/Winter Winter Spring Spring Mid-Spring Late Spring First we have CO2 ice from the atmosphere freezing onto the ground Orographic lifting forms a CO2 cloud that adiabatically cools forming fine grained CO2 snow (cold spot) on the downwind rim of the crater The CO2 ice sublimes significantly faster the CO2 snow Spring Mid-Spring Late Spring The CO2 snow then cold traps the surrounding H2O molecules forming an ice patch that covers the CO2 cold spot Add layer of CO2 ice under everything CO2 then sublimes from under the water ice patch (mid-spring) Late spring we are left with a patch of H2O water ice on the ground Spring/Summer CO2 Snow CO2 Ice The water ice patch has sublimed by the beginning of the summer H2O Ice

The Hypothesis of Cold Spot Formation Autumn/Winter Winter Spring Mid-Spring Late spring Add layer of CO2 ice under everything Spring/Summer The Hypothesis of Cold Spot Formation CO2 Snow CO2 Ice H2O Ice

Conclusions: We use THEMIS and TES data to show ice patch and cold spot correlation Successfully found 24 ice patches that have had cold spot activity earlier in the year Ice Patch activity repeats yearly for all 24 craters Future work would be to find many more craters with similar characteristics

THEMIS (Thermal Emission Imaging System) data 266E 70N 42E 69N NORTH NORTH Temp = 190K / 220K Ls = 54 (mid-spring) Earth time = May 2006 Mars year 17 Temp = 168K / 216K Ls = 61 (mid-spring) Earth time = June 2006 Mars year 17 NORTH NORTH Need a distribution slide before this (Location Map). Recheck mars years Ls = 62 (mid-spring) Earth time = July 2004 Mars year 16 Ls = 87 (end of spring) Earth time = August 2006 Mars year 17

THEMIS (Thermal Emission Imaging System) data 285E 69N 42E 69N NORTH IR image Temp = 225K / 235K IR image Temp = 168K / 216K NORTH Present the problem Visible image 285E 69N Visible image 42E 69N

Use this slide for corresponding IR and vis

THEMIS (Thermal Emission Imaging System) data 266E 70N 285E 69N NORTH IR image Temp = 190 K / 220 K IR image Temp = 227 K / 238 K NORTH Get rid of left crater (42E 69N) Visible image Visible image