page_title: Phase curve (astronomy)
section_title: Mars
hierarchical_section_title: Phase curve (astronomy) / Mars
caption_attribution_description: English: Phase curve of Mars
context_page_description: In astronomy a phase curve describes the brightness of a reflecting body as a function of its phase angle. The brightness usually refers the object's absolute magnitude, which, in turn, is its apparent magnitude at a distance of astronomical unit from the Earth and Sun. The phase angle equals the arc subtended by the observer and the sun as measured at the body.
  The phase curve is useful for characterizing an object's regolith and atmosphere. It is also the basis for computing the geometrical albedo and the Bond albedo of the body. In ephemeris generation, the phase curve is used in conjunction with the distances from the object to the Sun and the Earth to calculate the apparent magnitude.
context_section_description: Only about 50° of the martian phase curve can be observed from Earth because it orbits farther from the Sun than our planet. There is an opposition surge but it is less pronounced than that of Mercury. The rotation of bright and dark surface markings across its disk and variability of its atmospheric state (including its dust storms) superimpose variations on the phase curve. R. Schmude obtained many of the Mars brightness measurements used in a comprehensive phase curve analysis performed by A. Mallama.
  Because the orbit of Mars is considerably eccentric its brightness at opposition can range from magnitude −3.0 to −1.4. The minimum brightness is about magnitude +1.6 when Mars is on the opposite site of the Sun from the Earth. Rotational variations can elevate or suppress the brightness of Mars by 5% and global dust storms can increase its luminosity by 25%.
caption: The phase curve of Mars[18] compared to Mercury.[1]
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