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More Information On Mars Today Tool

1995 The Regents of the University of California

Mars Tool

Mars Today Tool created by Howard Houben

Try the Mars Today Page for more information and some really interesting animations!

Mars Today Poster Panels - What is Going On?

I. How does the orbit of Mars compare with the orbit of Earth?

[Beginning Level]
The panel above shows the current positions of Mars and Earth in their orbits around the Sun. The Sun is shown in the center of the panel. Note that Mars (shown in yellow) has a slightly more elliptical orbit compared to that of Earth (shown in blue).

[Advanced level]
For much of the time, Mars is too close to the Sun or behind the Sun (as viewed from Earth) to be observed by Earth-based telescopes. At certain points, however, Mars is near opposition (almost directly opposite the sun in the sky as seen from Earth) and can be observed throughout the night.

II. Relative Physical and Angular Sizes of the Earth and Mars

[Beginning level]
The panel above compares the relative angular sizes of Mars and the Earth. At any given time, this corresponds to the relative physical sizes of the two planets.

[Intermediate level]
This panel shows the relative size of the Martian disc as viewed from Earth compared to the size of Earth's disc viewed as though you were standing on Mars. (Since the diameter of Mars is about half that of the Earth, Mars appears to be about half the size of the Earth when viewed from the same distance.)

[Advanced level]
Both of these discs are compared to a circle 25 seconds of arc in diameter. This circle represents the largest possible apparent size of Mars as viewed from Earth (which is achieved only on those very rare occasions when the planets are both favorably positioned at the nearest points in their orbits). For comparison, note that the diameter of the full moon is approximately 1/2 a degree of arc. Also note that there are 3600 seconds of arc in a degree of arc.

III. What features are visible on Mars today?

[Beginning level]
The panel above displays a simulated image of Mars as it would appear at the present time to a very high resolution Earth-based telescope.

[Advanced level]
The statistics printed below the image indicate the apparent diameter of Mars (in seconds of arc); the angle between the Sun and the Earth as viewed from Mars (in degrees); an angular measure of the season in the Martian northern hemisphere (Ls= 0 at the vernal equinox, 90 at the summer solstice, 180 at the autumnal equinox, and 270 at the winter solstice); the sub-solar latitude in degrees (another indicator of the season); the longitude of the sub-Earth point in the image; and the latitude of the sub-Earth point.

IV. What is Mars weather like today?

The panel above shows a model prediction of the meteorology or weather at the present time (from the Ames Mars Climate Model). Daily average temperatures (in degrees Kelvin) in the lower atmosphere are color coded, while predicted wind speeds and directions are indicated by the arrows.

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All text, images, and other resources in this page are Copyright 1995, The Regents of the University of California. All rights reserved. For permission, email