Last Monday night there were numerous reports of a large meteor over Scotland. What is a meteor? And how can they help us unravel the secrets of the solar system?
Most meteors are tiny specks of dust from space that generate a bright trail in the sky as they enter the Earth’s atmosphere. The largest meteors – often called fireballs – can sometimes even result in meteorites landing on the ground (note, a meteorite is what a meteor becomes once it has hit the ground; a meteor is what a meteoroid becomes once it enters the Earth’s atmosphere).
Meteorites are rocky time capsules from space that are a record of conditions in the solar system ~4.6 billion years ago. At the moment it is still unclear whether the fireball over Scotland was large enough to produce meteorites, and if so where these may have landed.
The chances of a meteorite falling are the same everywhere on the Earth. Unfortunately this means that most meteorites end up in the oceans, or land in remote areas where few people see the preceding fireball. If they fall in more densely populated areas, such as Scotland or Chelyabinsk in Russia, then the eyewitness accounts and videos can be used to piece together the object’s size, velocity, direction and potential point of impact with the Earth.
Even then, the local terrain can make recovering a meteorite extremely challenging. We aim to collect meteorites as quickly as possible after they are seen to fall in order to minimise exposure to the terrestrial environment.
Out of a collection of ~50,000 meteorites worldwide, fewer than 10 have been observed falling to Earth in enough detail to accurately calculate where in the solar system they came from. However, this number is increasing as more fireball camera networks, many of which are run by amateur astronomers, are set-up around the world. We even have our own camera on the roof of the Museum here in South Kensington.
Although we haven’t seen any large fireballs (yet!), we have recorded plenty of smaller meteors in the London sky. Data from our camera is then fed into the UK Meteor Observation Network (UKMON) and is being used to understand the origin of extra-terrestrial materials that arrive on Earth.