Observing Mars By Brad Jarvis

Overview Basic facts Orbits and distance Viewing Mars from Earth The view from space Current exploration Conclusion References

Basic Facts about Mars Location is fourth from the Sun Day is about the same as an Earth day Year is nearly two Earth years long Size is half Earth’s, with about the same land area Gravity is about 1/3 that of Earth Atmosphere is mostly CO 2 at less than 1% the air pressure on Earth Temperature is -125°F to -13°F Two moons are possibly captured asteroids

Orbits and Distance Mars is: million miles away from Earth at opposition million miles away from the Sun

Viewing Mars from Earth

Viewing Mars from Earth Apparent Size The apparent size of Mars varies between 14 and 25 arcseconds at opposition (1/133 and 1/75 the apparent size of the Moon)

Viewing Mars from Earth Albedo Features Common types of features: Lacus (lake), Mare (sea), Regio (region), Sinus (bay) Map courtesy Daniel Troiani (producer), Carlos Hernandez (named features), ALPO

Viewing Mars from Earth The Colors of Mars Red is the color of iron-rich dust Dark gray is the color of volcanic rock White is the color of ice

Viewing Mars from Earth Changes in Appearance Apparent tilt of poles varies with relative positions of Earth and Mars Sizes of polar regions get smaller in summer and larger in winter Clouds can be white (water and CO 2 ice) or red (dust) Dust storms usually occur in southern summer and may engulf the planet Features appear dark or light depending on presence of dust

The View from Space Dust storm from Hubble Space Telescope

The View from Space A Confusion of Orientation Earth-based photos and maps are oriented so that south is up Space-based photos and maps are oriented so that north is up There have been two different longitude references for space- based maps since 2002

The View from Space Mapping the Surface Common types of features: Chasma (chasm), Fossa (long valley), Mons (mountain), Patera (crater), Planitia (plain), Planum (plateau), Terra (land), Tholus (hill), Vallis (valley), Vastitas (lowland)

The View from Space Martian Geology

The View from Space: Martian Geology Cratered Terrain Older parts of Mars are heavily cratered Typically in the southern hemisphere Noachis Terra (Noachis)

The View from Space: Martian Geology Northern Plains Younger parts of Mars are lightly cratered Typically in the northern hemisphere

The View from Space: Martian Geology Channels and “Canals” Water likely carved channels in the surface Some of the famous “canals” seen from Earth may have dust blown by the wind Xanthe Terra (Oxia Pallus)

The View from Space: Martian Geology Valles Marineris Valles Marineris is the largest canyon in the Solar System. It is the width of the lower 48 states of the U.S. and up to four miles deep. It is a fracture caused by the uplift of volcanoes in the Tharsis region.

The View from Space: Martian Geology Tharsis and Olympus Mons Tharsis is a region where the crust has uplifted. It is about 2,500 miles across and six miles high. Sitting atop this uplift are shield volcanoes, the largest of which is Olympus Mons. It is over 300 miles across, and 15 miles high.

The View from Space: Martian Geology Hellas Hellas Planitia is one of two large impact basins (Argyre Planitia is the other). It is 1,100 miles across and five miles deep. It is full of fast-cooling dust. It has been seen with frost and haze in the mornings.

Current Exploration Two Mars Exploration Rovers (left) will land on opposite sides of Mars in January They will study rocks over a maximum range of about 3/4 mile per day. Mars Express (including an orbiter and lander, right) will arrive at Mars in December It is the first mission since Viking to look for life.

Conclusion Mars is an entire world, with the same amount of land as Earth, and it is only six months away. It is an interesting place that can be explored by telescope, by robot, and eventually by people.

References Books: Boyce, J. (2002). The Smithsonian Book of Mars. Washington: Smithsonian Institution Press. Beatty, J., Petersen, C., Chaikin, A., eds. (1999). The New Solar System, 4th Ed. Cambridge: Sky Publishing Corp. Hartmann, W. (2003). A Traveler’s Guide to Mars. NY: Workman Publishing. Web: ALPO Albedo Map [ Mars Exploration Rover [ Mars Express [ Mars Gazetteer [ Mars Section Observing Alert and Images Page [ Mars Society [ Software: Starry Night Pro (Space.com) The Guide (Project Pluto)

Photos Courtesy: Tim Brown