Comet Shoemaker-Levy 9 hits Jupiter

July 1994: a comet torn apart by Jupiter's tides crashes into it in 21 pieces, leaving dark scars almost as wide as Earth

Watch it in 3D

Step by step

Caught by Jupiter

Most comets go round the Sun. This one, a loose ball of ice and dust a few kilometres across at most, came near Jupiter slowly enough for the giant planet's gravity to take it over. Working back along its path, astronomers found that it was probably caught in the early 1970s, perhaps as early as the mid-1960s.

A string of pearls

The comet was found on the night of 24 March 1993 with the 46 cm Schmidt telescope on Palomar Mountain in California, while the three were searching for asteroids that come near Earth. It was their ninth periodic comet, hence its name. The first photographs showed a strange squashed comet, and sharper telescopes soon split it into a line of points.

What it taught us

For the first time people watched two bodies of the Solar System collide. It showed that comets really do hit planets, and how Jupiter's gravity sweeps many of them up.

Chains of craters on Jupiter's moons Callisto and Ganymede, long a puzzle, now made sense: comets torn apart by Jupiter before they struck. Whether Jupiter shields Earth overall is still argued, as it removes many comets but also sends some towards the inner planets. The impacts made the danger to Earth feel real, and helped start the search for asteroids that could hit it.

It still happens

Jupiter is still being hit. In 2009 an amateur astronomer found a new dark scar, and since 2010 amateurs filming Jupiter have caught the flashes of small bodies striking it.

On 19 July 2009, fifteen years almost to the day after the first impact, the Australian amateur Anthony Wesley spotted a new dark spot in Jupiter's southern hemisphere, left by an asteroid or comet probably a few hundred metres across. On 3 June 2010 he and Christopher Go, in the Philippines, filmed a flash lasting about two seconds, from a body only about ten metres across.

Objects in this story

Jupiter