albedo

Mars is the fourth planet from the Sun. Mars' diameter is 6,790 km and takes 687 days to orbit the Sun. Mars is named after the Roman god of war. In Eastern Asian cultures Mars is ...

Fobos

Astronomy; Mars

The larger and innermost of the planet Mars' two moons. Phobos was discovered by Asaph Hall on August 17, 1877. In Greek mythology, Phobos was the son of Ares (Mars) and Aphrodite ...

radiación ultravioleta

Astronomy; Mars

The invisible electromagnetic radiation beyond the violet end of the spectrum of visible light, of wavelengths ranging, roughly, from 4000 down to 400 angstroms.

solsticio de invierno

Astronomy; Mars

The position on the ecliptic occupied by the sun about december 22 when it reaches its greatest southerly declination.

rayos X

Astronomy; Mars

Very short wavelength radiations beyond the ultraviolet in the spectrum, which are about one ten-thousandth as long as the visible violet and are extremely penetrating.

cenit

Astronomy; Mars

The point of the celestial sphere directly overhead, 90 degrees above the horizon, for any point on earth; it is the point where a plumb line extended upward would intersect the ...