Mars will never look as big as the full Moon. But it isn’t even the biggest planet.
From humanity’s perspective, the Sun and Moon always dominate Earth’s skies.
They outshine everything in terms of brightness, with superior appearances in terms of angular size: around 30′ (arc-minutes): half a degree.
All the planets in our Solar System are only somewhat larger than the Moon, but much farther away.
When they’re closest to Earth, they appear largest.
But their angular sizes all vary as the planets orbit relative to one another.
Mercury, the smallest planet, varies from 4.5″ to 13″, where 1″ (arc-second) is 1/3600th of a degree.
Both Neptune (from 2.2″ to 2.4″) and Uranus (from 3.3″ to 4.1″) always appear even smaller.
Their much greater distances from Earth ensure that.
Mars experiences the greatest relative variation in angular size, from 3.5″ to 25.1″.
Saturn, the second-largest planet, ranges from 14.5″ to 20.1″, but if you include its main rings, becomes enormous, spanning from 33.8″ to 46.9″.
Jupiter is the largest planet, residing quite far from Earth.
For angular size, it ranges between 29.8″ and 46.9″.
Venus, our sister planet, comes closest to Earth, ranging from 9.7″ to a whopping 66.0″.
Humans with exceptional vision, at Venus’ closest approach, can barely discern its crescent phase without a telescope.
Mostly Mute Monday tells the astronomical story of an object, event, class, or phenomenon in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.