and show similar tilts in

their rotational axes that give them strong seasonal variability; and

historic evidence of changes in climate.

In this animation, we see both planets in true color first, then draped in false color, showing relative altitudes of surface features. Blues indicates low features; reds and whites indicate high features.

http://svs.gsfc.nasa.gov/stories/mars_earth_20040421/images/item02.mpg

Earth versus Mars:The two planets have striking similarities. They have … roughly the same amount of land surface area; relatively similar atmospheric chemistry; and large, sustained polar caps comprising water ice;

Indeed, Earth’s dry valleys do look similar to those on Mars. For instance, Indeed, Earth’s dry valleys do look similar to those on Mars. For instance, in this animation, we plunge from space down to a remarkable scene in in this animation, we plunge from space down to a remarkable scene in Antarctica, the Don Juan Pond, one of the saltiest, coldest bodies of water Antarctica, the Don Juan Pond, one of the saltiest, coldest bodies of water on Earth. In the first scene the camera slides down the valley slope and on Earth. In the first scene the camera slides down the valley slope and stops above the actual pond of sub-freezing water at the base. We see thestops above the actual pond of sub-freezing water at the base. We see thecrinkled folds and crinkled folds and dug outdug out rivulets rivulets and gullies eroded and gullies eroded into the landscape. into the landscape. They serve as the They serve as the signs of surface signs of surface erosion and are erosion and are analogous to the analogous to the kinds of tell-tale kinds of tell-tale signatures that signatures that Mars experts want Mars experts want to study more to study more thoroughly for the thoroughly for the signs of a wetter signs of a wetter Martian past.Martian past.http://svs.gsfc.nasa.gov/stories/mars_earth_20040421/images/item04b.mpg

Evidence of Surface Water: Earth Deltas, Martian Deltas

These images compares how evidence of water appears on Earth,

offering clues as to where we might look for itspresence on Mars.

The first two sequences here depict (a) the mouth of the Colorado River in the Mexican Baja, and (b) the Lena River Delta in Russia. Data for these scenes come from the Landsat 7 spacecraft. As for Mars, we see here the so-called “Distributary Fan” located northeast of Holden Crater. As seen from Martian orbit by the Mars Orbiting Camera flying on the Mars Global Surveyor spacecraft, this dramatic visualization shows us where liquid water likely flowed across the Martian surface sometime in the planet’s past.

http://svs.gsfc.nasa.gov/stories/mars_earth_20040421/images/item06.mpg

On Mars, scientists are looking for signs of life in the planet’s past. Unlike the Earth, Mars is no longer a hospitable place for life, because it is generally bathed in a lethal dose of cosmic radiation, not to mention high energy the particles blown by solar wind. It is also cold and dry, with no ready availability of water.

The Earth bursts with life, with carbon as life’s proxy, because life as we know it basically implies transactions in carbohydrates (CH2O). A thorough understanding of the Earth’s carbon cycle is therefore vital to a search for life elsewhere in the universe. The undulating colors in these scenes come from NASA’s SeaWiFS instrument. They show the cycle of life as it ebbs and flows through the carbon cycle. The pulse of this carbon uptake is reflected in the oscillation of chlorophyll concentrations, depicted by this intuitive false color representation.

http://svs.gsfc.nasa.gov/stories/mars_earth_20040421/images/ElanVital.mpg

Magnetic Signatures:Mars does not have the same kind of magnetic field as Earth. But evidence collected by the Mars Global Surveyor (MGS) indicates that the planet may have once had a global magnetic field, generated by

an internal dynamo. Evidence suggests that the planet’s magnetic field reversed direction, or flipped, several times in its early days as conditions in the mantle and core of the planet changed. But that dynamo faded, leaving only faint traces of its magnetic past locked in the Martian crust.

http://svs.gsfc.nasa.gov/stories/mars_earth_20040421/images/MagSignitures.mpg

Some Basic Facts about Earth• Ave. Solar Distance: 149,600,000 km (1AU) • Diameter: 12756.34 km • Rotational Period (one day): 23 hours, 57 minutes • Mean Surface Temp: 14_ C • Orbital Period (one year): 365.242 Earth days • Moons: 1 (Luna) • Gravity: 9.78 (m/s2) Earth

Some Basic Facts about MarsAve. Solar Distance: 227,940,000 km (1.52 AU) Diameter: 6,794 km Rotational Period (one day): 24.622 hours • • • Mean Surface Temp: -63_ C • Orbital Period (one year): 686.98 days • Moons: 2 (Phobos and Demios) • Gravity: 38% Earth