What are meteorites?

Meteorites are interplanetary debris that falls to Earth, some of which have been known to have come from the Moon or Mars. These meteorites reveal otherwise unknown characteristics of their parent objects, shedding light on what they are like.

For example, in a study, researchers report that basaltic meteorites contain mineral grains containing helium and argon isotopes which indicate that these minerals spent millions of years exposed to cosmic rays before being incorporated into larger protoplanets and ultimately became part of the basaltic rocks we see today.

Meteor Shooting Star Perseid  - Hans / Pixabay
Hans / Pixabay

Understanding how long it took for rocks to become exposed to space can inform us about how bodies formed and how they evolved over time.

Pre-solar grains in meteorites

Some meteorites are thought to contain materials from when the solar system formed, known as pre-solar grains.

Pre-solar grains are particles that predate the formation of our solar system and are thought to be building blocks of stars. These grains are rare, and not present in every meteorite, but their discovery has helped us understand more about the origin of the early solar system.

Milky Way Stars Sky Universe  - Hans / Pixabay
Hans / Pixabay

The pre-solar grains in meteorites can give scientists clues about what materials were present before our Solar System’s formation and clues about the ages of stars.

Pre-solar grains are the most primitive material in our Solar System. These small particles of stardust came into existence at the same time as stars, before even dust and gas clouds formed. It is therefore likely that they represent a window to the state of our Universe before the formation of our Solar System. Studying these grains is therefore one way to understand more about how our Universe was created and what it was like before our Sun and planets were born.

It’s important to note that pre-solar grains have a very different origin than interstellar grains, which are created in the dense environment around dying stars. In contrast, pre-solar grains originate from inside stars when nuclear fusion reactions occur within them. This means that many different types of pre-solar grain exist because each grain has a different stellar origin based on the type of star it formed in.

There are three main ways scientists study pre-solar grains: electron microscopy, mass spectrometry, and synchrotron x-ray radiation analysis. The first two methods enable scientists to determine the composition of each grain with extreme accuracy by analyzing how electrons bounce off each individual particle or how ions interact with them when exposed to x-rays respectively. Studies from Radiation analysis give scientists an understanding of how many atoms there are in each grain and help us determine their chemical composition as well as their size distribution and even internal structure!

Age of solar system

When the Solar System formed 4.6 billion years ago, it was a chaotic place with collisions between large objects happening frequently.

solar system
solar system in a row

An age for our Solar System was determined by measuring isotopes of lead in various meteorites.

The age of the solar system was determined by measuring the ratio of two isotopes of lead in meteorites. The two isotopes are 208Pb and 207Pb. Because they are stable and do not decay over time, their natural abundance ratios can be used as a “clock” to determine how long ago they were formed by the radioactive decay of other elements inside stars. The fact that we know the half-life of uranium-235 (the parent element) allows us to easily calculate the age given a specific ratio of 208Pb/207Pb in any rock or meteorite.

Can the isotopes of lead be used for determining the age of substances?

The answer to that question lies in the properties of lead, which is used in radioactive dating. Lead was one of the elements discovered by alchemy.

Because Lead has a relatively low melting point, lead is easy to cast into molds and can be used for all sorts of things, such as pipes and shield covers.

Lead’s usefulness led to it being mined extensively over the centuries, giving us today what we call “metals” and “non-metals”. And yet no one knew about its radioactive properties until the early twentieth century when researchers working on nuclear reactions found that substances containing lead could emit radiation. This discovery led them to look at how long these substances would remain radioactive before becoming stable again.

Isotopes are different forms of a given element but with different atomic weights or numbers (e.g., carbon-12 and carbon-14).

How old is the Earth?

  • The date is based on a measurement of lead isotopes in meteorites.
  • This analysis gave a date of 4.565 billion years for the age of the Solar System (hence making rocks on Earth over 4 billion years old).
  • The age of the solar system is our best guess at the age of Earth because we don’t have many ways to directly measure Earth’s age.

Meteorites are rich in stardust. They contain tiny grains of mineral condensates called pre-solar grains which formed before the solar system was formed. Planets like Earth would have accreted later on by accretion of material into large bodies (planetesimals) and subsequent collisions between those bodies to form a planet such as the Earth.

Contribution from the Kepler space telescope

We now know that stellar systems similar to our own are common throughout the Universe!

Thanks to the Kepler space telescope, we now know that stellar systems similar to our own are common throughout the Universe! The Kepler mission has discovered thousands of exoplanets—planets orbiting other stars—many of which are similar to Earth in mass and orbit. In fact, the Kepler space telescope has found numerous planets that are Earth-sized and orbiting in their star’s habitable zone (although this does not mean they actually have liquid water).

In addition, the Kepler mission helped us determine how many planets there are in our galaxy. This will allow us to estimate how many habitable worlds there may be in our Milky Way galaxy.

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