Ask Astro: Can Phobos and Deimos be seen from the surface of Mars?

Each martian moons, Phobos and Deimos, may be seen from the floor. They even visibly bear phases like our personal Moon.

Can Phobos and Deimos be seen from the floor of Mars? If that’s the case, do they exhibit phases like Earth’s Moon?

John Carlson
Colon, Michigan

In brief: Sure and sure! Each Phobos and Deimos are seen from the martian floor. Phobos is far brighter, as it’s each bodily bigger and orbits a lot nearer to the planet than Deimos. Phobos will seem within the martian sky as shiny as magnitude –9 this month, whereas Deimos will peak at magnitude –5.

Phobos is so near Mars and orbits so shortly — roughly as soon as each seven hours and 39 minutes, or about thrice per martian day — that it’ll noticeably wax or wane throughout a single look (not like our Moon, which seems to rise and set in the identical section). Additionally, Phobos seems giant sufficient — some one-third to one-half the scale of the Full Moon at occasions — {that a} cautious observer will be aware it isn’t spherical. It’s seen for about 4 hours at a time and may be seen from a lot of the planet no less than as soon as per evening. Phobos can be shiny sufficient to identify at occasions through the day.

Deimos orbits about 4 occasions farther from Mars than Phobos does and seems roughly 2.5′ throughout (about twice the utmost dimension of Venus as seen from Earth). This moon is usually invisible through the day however remains to be brighter than any star within the evening sky. It could look spherical to the bare eye as a result of it’s extra spherical than Phobos and due to its smaller angular dimension. Deimos takes simply over 30 hours to orbit; it seems for a couple of days at a time, then disappears for a couple of extra earlier than the cycle repeats. It stays above the horizon for about 60 hours at a time, transferring slowly from east to west (whereas Phobos seems to zip from west to east). Deimos goes by way of a full set of phases roughly twice from moonrise to moonset however as a result of it’s so small, you’d want a telescope to see these phases change. As a substitute, you may discover it rising brighter because it progresses towards full and fainter because it wanes towards new.

Alison Klesman
Senior Editor


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