Dates for your saved location. About every 26 months Mars slips behind the Sun’s glare for a while, then reappears in the morning sky.
Getting Closer
How big Mars looks through a telescope, over the next ten years. Every 26 months Earth overtakes Mars on the inside track and the gap closes — an opposition. Because Mars’s orbit is lopsided, some passes are far closer than others.
Olympus Mons
The tallest volcano in the solar system — a shield volcano like those of Hawaii, grown enormous because Mars has no moving plates to carry it away from the hot spot beneath. Lava piled up in the same place for billions of years.
How tall
How wide — laid over Utah
Height
21.9 km
2½ times Everest
Width
600 km
Wider than Utah is tall
Summit caldera
80 × 60 km
Up to 3 km deep
Edge cliffs
Up to 8 km
A steep scarp around much of its base
Its slopes are only a few degrees on average, so climbing it would feel like a very long, gentle walk — and it is so broad that from its edge the summit would sit beyond the horizon. Some of its lava flows may be only a few million years old.
More Landmarks
Valles Marineris
A canyon system 4,000 km long and up to 7 km deep — it would stretch from Los Angeles to New York. The whole Grand Canyon would fit inside one of its side branches.
Tharsis
A volcanic plateau some 4,000 km across, topped by three more giant volcanoes in a row — Arsia, Pavonis and Ascraeus Mons — with Olympus Mons off its western edge.
Hellas Basin
An impact scar 2,300 km wide and over 7 km deep — the lowest place on Mars. Often filled with frost or cloud, so it can look bright in a telescope.
The polar caps
Water ice capped by a winter layer of frozen carbon dioxide. A cap is usually the first detail you notice in a small telescope, and it visibly shrinks through the Martian spring.
Syrtis Major
A dark plain of volcanic rock — the first surface feature ever recorded on another planet, sketched by Christiaan Huygens in 1659. Easy to spot in a small telescope when it faces us.
Jezero Crater
An old lake bed with a river delta, where NASA’s Perseverance rover landed in 2021 to search for signs of ancient life. See it in 3D ›
The Two Moons
Phobos 27 km long · orbits in 7 hours 39 minutes — faster than Mars spins, so from the surface it rises in the west and sets in the east, twice a day. It is spiralling inward and is expected to break apart or crash into Mars within about 50 million years.
Deimos 15 km long · orbits in 30.3 hours. From Mars it would look like a bright star, barely a disc at all.
Both are dark and lumpy. They look like captured asteroids, though they may be debris from a giant impact — Japan’s MMX mission aims to find out. Discovered in 1877 and named for the sons of Ares: Fear and Dread. Near opposition they can be glimpsed in larger telescopes if Mars’s glare is kept out of view.
The Planet Itself
Diameter
6,779 km
About half of Earth
Day
24h 40m
One sol — remarkably Earth-like
Year
687 days
Nearly two Earth years
Gravity
38%
You’d weigh a bit over a third
Air
95% CO₂
Under 1% of Earth’s pressure
Temperature
−153 to 20 °C
Polar night to summer noon
Mars is red because its dust is rusted — iron oxidised over billions of years. Through a small telescope near opposition, look for a white polar cap and dark markings like Syrtis Major rotating slowly into view; Mars turns only a little slower than Earth, so the same face comes back about 40 minutes later each night.