Which planet has the largest volcano in the solar system?

1. Olympus Mons: the giant on Mars

Olympus Mons is consistently identified in scientific and popular references as the Solar System’s largest volcano: NASA, Britannica and multiple astronomy outlets report a summit rise of roughly 21–22 km above the surrounding plains and a basal diameter on the order of hundreds of kilometres, making it many times the size of Earth’s largest volcanoes ^{[1] [2] [3]}.

2. How “largest” is being measured — height, width, area, volume

Different sources emphasize different dimensions: some cite height (about 21.9–22 km), others cite width (roughly 370–700 km) or area (≈300,000 km²), and one study estimated the volcano’s volume at about 4 million km³ — roughly 100 times the volume of Mauna Loa — so “largest” is supported across multiple metrics ^{[1] [2] [5] [3]}.

3. Why Mars allowed a monster to grow

Researchers point to Mars’ weak gravity and lack of plate tectonics as the primary reasons Olympus Mons could grow so large: a fixed crust over a long-lived hotspot lets lava accumulate in one place for millions to billions of years, producing the wide, gently sloping shield volcano seen today ^{[1] [3]}.

4. Scientific debate and open questions about Olympus Mons’ history

Despite consensus on size, scientists debate details of the volcano’s growth and environment. Rice University coverage highlights active scientific discussion over the volcano’s escarpment formation and whether some features reflect interactions with water or episodic collapse, showing ongoing research about its geologic history ^{[6] [7]}.

5. Comparisons with other Solar System mountains and volcanoes

Olympus Mons is usually ranked as the tallest volcano and tallest mountain on Mars and the Solar System’s largest volcano; some sources note it is “approximately tied” with Vesta’s Rheasilvia for highest known elevation when measured differently, reflecting how measurement choices affect rankings ^{[1] [2]}.

6. Public reporting and simple summaries — broad agreement

Major popular science outlets (BBC Sky at Night, Space.com, Astronomy Magazine, and others) and educational institutions repeat the same headline: Olympus Mons is the largest volcano in the Solar System. These summaries align on the central fact while varying in the figures they present ^{[8] [4] [5] [9]}.

7. Limits of current claims — “largest known” vs. absolute finality

Most sources present Olympus Mons as the largest volcano known or the largest in the Solar System; explicit hedging about future discoveries is not prominent in the sampled reporting, but some commentaries acknowledge the provisional nature of rankings in a still-explored Solar System ^{[1] [7]}.

8. Practical implication: what “largest volcano” teaches us

Studying Olympus Mons helps scientists understand volcanic processes without plate tectonics, planetary heat budgets, and landscape evolution under different gravity and atmospheric conditions — insights applicable to comparative planetology and to interpreting volcanic features elsewhere ^{[1] [3] [6]}.

Limitations and sourcing note: this account is based solely on the provided set of sources, which uniformly identify Olympus Mons on Mars as the Solar System’s largest volcano and provide the cited figures; available sources do not mention any authenticated discovery of a larger volcano elsewhere ^{[8] [4] [6] [3] [1] [2] [5]}.