1

Surface Conditions

• Surface temperature averages -63oC, but typically varies from -89oC to -31oC.– the Viking landers occasionally

measured temperatures > 0oC, and atleast once up to 80oF.

• Surface Gravity: 3.7 m/s2 (0.38 G)

• Albedo: 0.15

• Solar Irradiance 589 W/m2 (43% of earth)68

2

Mars’ Atmosphere

95.3% CO2 and 2.7% N2, with 1.6% Ar and small a amount of O2 (0.13%).

This is almost the same composition as what other planet’s atmosphere?

69

3

70

4

Atmospheric Pressure• The pressure of the atmosphere on Mars

is only about 7 millibars. The average pressure on Earth is about 1000 millibars.

• When the air pressure is this low, liquid water simply boils into water vapor.

• This explains why no liquid water can exist on the surface of Mars today. But who knows about under the surface….

71

5

Weather Conditions

• With the low temperatures, low barometric pressure and almost no water vapor, the most common type of “weather” on Mars is dust storms!

72

6

73

7

74

8www.spacescience.org/ExploringSpace/Gallery/MercerPaintings/MarsDustStorm213.JPG

75

9

Precipitation! – NOT!

• No precipitation falls on Mars, at least not in the same way it does on Earth - no rain, no snow, no sleet.

• Sometimes frost does form on the rocks.

76

10Probably solid CO2 77

11

78

12

Weather Forecast

• Despite the very thin atmosphere, Mars has very active weather

– Winds of 2 to 30 m/s (67 mph)

– Local & planet-wide dust storms

– Frost in low-elevation areas

– Dust devils (next 2 slides)

– Southern polar cap sublimation of CO2 adds atmosphere in S.H. summer.

79

13

80

14

81

15

The Polar Ice Caps

• The northern ice cap is made up mostly of frozen water ice – just like on earth!

• The southern cap is water ice underneath, but there’s a thick layer of dry ice (frozen carbon dioxide) over the water ice.

82

16

The ice caps shrink and grow with the seasons.All of this material goes into the atmosphere,doubling the air pressure in summer.

btc.montana.edu

83

17

Local winter tosummer changes inthe south polar “ice”cap (frozen CO2)

Part of Mars’atmosphere islying frozen on itssurface!

84

18

June, 2003 Oct, 2003

85

19

86

20

Layersresult fromsublimationandfreezingcycles.

North polarcap.

87