Mars and the Moon will play hide-and-seek for much of the year. The Moon will pass in front of the Red Planet four times, briefly hiding it from view. From the United States, the best of those events takes place tonight. Mars will disappear from view from Florida across Texas to southern California.

Such an event is called an occultation. That’s from a Latin word that means “to hide.” Occultations are possible because the orbits of both Mars and the Moon lie near the ecliptic, which is the Sun’s path across the sky. Both bodies wander away from the ecliptic a little, though, so most months the Moon passes within a few degrees of Mars but doesn’t cover it up.

Even when the two bodies do line up, though, it’s visible from limited regions. In part, that’s because an occultation lasts only an hour or two, so from most of Earth it happens when Mars and the Moon are below the horizon. And the Moon is much closer to us than Mars is, so most regions see the Moon pass above or below Mars — with no occultation at all.

Tonight, though, the geometry will be just right from the southern United States. The Moon will cover Mars before midnight, and the Red Planet will remain hidden for up to a couple of hours.

The rest of the country will miss out on the occultation, but will still see a beautiful sight. Mars looks like a brilliant orange star quite near the Moon throughout the night.

More about the Moon and Mars tomorrow.

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