#Micrometeorites
Space dust that reaches the ground: cosmic spherules, unmelted particles, where they are collected and how to search safely yourself.
Micrometeorites are extraterrestrial particles smaller than about 2 mm that survive the fall through the atmosphere. Most are a tenth to a few tenths of a millimetre across, and thousands of tonnes reach the ground every year, far more than all larger meteorites together.
Most began as dust shed by comets or ground off asteroids in collisions. Some melted on the way down into tiny balls called cosmic spherules; others survived unmelted and keep carbon-rich material and grains older than the Sun.
Scientists collect them from Antarctic snow and ice, deep-sea clay, deserts, the stratosphere and ancient rocks, and since 2016 they have been identified in sediment from city roofs, so anyone with a magnet and a microscope can search for them.
Part of Meteorites across the sciences.
Courses (1)
- What falls from the skyEvery day Earth sweeps up tonnes of material from space, almost all of it as dust. This lesson sets out the vocabulary and the scale of what
Space missions (1)
- Comet InterceptorA mission that will wait in space for a pristine comet, then split into three to meet it.
Glossary (3)
Questions and answers (15)
- Can I find meteorites in my garden?It's possible but very unlikely. Meteorites have occasionally landed in gardens, but most garden 'meteorites' turn out to be sla
- Can I find meteorites in the UK?It's possible but rare. Britain's wet climate makes meteorites rust away and its green landscape hides them, so almost all British m
- Can meteorites come from comets?Possibly, in rare cases, but no meteorite has been proven to come from a comet. Comet dust is fragile and fast, so it usually burns up as me
- Can micrometeorites tell us about Earth's ancient atmosphere?Yes. Tiny micrometeorites preserved in 2.7-billion-year-old rocks were oxidised as they fell, suggesting the upper atmosphere then contained
- Can pupils hunt for micrometeorites at school?Yes, with care. Collecting dust from a roof gutter and searching it with a magnet and microscope is a real research technique, but genuine m
- Do meteorites contain sugars or DNA building blocks?Yes. Some carbonaceous meteorites contain sugars, including ribose, and nucleobases used in DNA and RNA, though not DNA itself.
- How do scientists stop meteorites being contaminated?By collecting fresh falls quickly with clean tools, storing samples in dry nitrogen or vacuum, using clean rooms, and checking isotopes to t
- How much space material lands on Earth each year?Estimates vary, but thousands of tonnes of extraterrestrial material reach Earth every year, almost all of it as tiny dust grains rather tha
- Is there space dust in my house?Very probably, a tiny amount. Thousands of tonnes of space dust land on Earth every year, and a few grains could settle anywhere, even on yo
- What are cosmic spherules?Cosmic spherules are tiny melted droplets of space dust, usually less than a millimetre across, that solidified as they fell through Earth&#
- What are interplanetary dust particles?Interplanetary dust particles are tiny grains collected in Earth's stratosphere by high-flying aircraft; many come from comets and are a
- What are micrometeorites and can I collect them?Micrometeorites are tiny particles of space dust, smaller than about 2 mm, that survive their fall to Earth.
- What happens to a meteorite as it weathers on Earth?Water and air rust its metal, alter its minerals and fill its cracks with Earth minerals. Over thousands of years, it crumbles and eventuall
- What is space weathering?Space weathering is the slow change of airless surfaces, such as the Moon and asteroids, caused by solar wind, cosmic rays and micrometeorit
- Why are witnessed falls more useful to science than finds?Falls are fresh, unweathered and unbiased by searching, often with known orbits, so they give the clearest view of what reaches Earth and of
Micrometeorites (20)
- Micrometeorites from Antarctic ice and snowThe cleanest, best-preserved micrometeorites come from the polar ice sheets, where there is almost no Earthly dust to hide them and the cold
- Cosmic dust collected by space missionsTo be sure exactly where a grain of dust came from, you have to fetch it yourself.
- Cosmic spherules: space dust melted into tiny ballsCosmic spherules are micrometeorites that melted completely as they entered the air and froze again as tiny balls.
- Micrometeorites from the deep sea and the desertsThe first micrometeorites ever recognised came from the bottom of the ocean. The deep-sea floor and the world's driest deserts are still
- Entry and survival: how a speck of dust reaches the groundA micrometeoroid hits the top of the atmosphere at more than 11 km/s. Within a few seconds it is braked, heated and either vaporised, melted
- Equipment and photography for micrometeorite huntingA micrometeorite hunt needs only modest equipment to begin, but good optics and lighting make the difference between seeing a black dot and
- Fossil micrometeorites and the air of the ancient EarthMicrometeorites trapped in ancient rocks are tiny probes of the past. Iron spherules 2.7 billion years old have been used to test what the u
- How much space dust falls on Earth each year?Thousands of tonnes of micrometeorites reach the ground every year. The exact figure is surprisingly hard to pin down, and different methods
- Micrometeorites: questions and answersShort, clear answers to the questions people ask most about micrometeorites, from whether they are dangerous to whether you can sell one.
- The people who opened up the study of micrometeoritesFrom Victorian oceanographers to a jazz guitarist, a small number of people turned space dust from a curiosity into a major field of planeta
- What micrometeorites reveal about the early Solar SystemMicrometeorites carry material from many more comets and asteroids than the meteorites in our museums, including fragile, carbon-rich bodies
- Recognising a micrometeorite, and telling it from industrial spherulesAlmost every tiny magnetic ball you find will be man-made or natural Earth material.
- Scoriaceous, unmelted and ultracarbonaceous micrometeoritesNot every micrometeorite melts. Some arrive gently enough to keep the minerals, textures and even the organic matter they had in space, maki
- How to search for micrometeorites yourself, safelyYou do not need to go to Antarctica. With permission, a bucket of sediment from the foot of a downpipe, some water, a magnet, sieves and a m
- Catching space dust in the stratosphereThe smallest space dust can be caught before it ever touches the ground. Since the 1970s, high-flying aircraft have collected interplanetary
- Types of micrometeoriteMicrometeorites are classified first by how much they were heated on the way down, and then by what they are made of.
- Micrometeorites in towns and citiesFor decades, scientists believed micrometeorites could never be picked out of city dirt.
- Water and the ingredients of life: did space dust deliver them?Every year, micrometeorites drop tonnes of carbon and water-bearing minerals onto the Earth.
- What are micrometeorites?Micrometeorites are tiny pieces of rock and metal from space, smaller than about 2 mm, that have survived the fall through Earth's atmos
- Where do micrometeorites come from?Micrometeorites begin as dust shed by comets and ground off asteroids in collisions.
People (2)
- Donald BrownleeThe astronomer who first collected dust from comets and asteroids in the stratosphere, and who led NASA's Stardust mission to a comet. D
- Michael ZolenskyThe NASA curator of cosmic dust who found liquid water from an asteroid inside salt crystals in the Monahans meteorite. Michael E.