A collection of small, clear quartz crystals unearthed in South Africa has given researchers from the University of Rochester a new clue about when our planet’s magnetic field formed. In the northern Limpopo province of South Africa, an arid, rocky terrain called Barberton Mountain Land has some of Earth’s oldest exposed stone—some more than three billion years old. By studying magnetized metal particles within ancient quartz found there, researchers discovered that the crystals formed in the presence of Earth’s magnetic field. The field that enveloped the planet at that time was only about half as strong as it is today, the scientists say. This discovery implies that our planet generated a weak magnetic field as far back as 3.4 billion years ago, well before the atmosphere became rich with oxygen (about 2.3 billion years ago).

This force field protected our young planet from high-energy charged particles in the solar wind and high-energy radiation emanating from the Sun. Now, billions of years later, this magnetic field sustains our current atmosphere. Without the protective shielding, charged particles streaming from the Sun would rip apart the water and oxygen in our atmosphere. Researchers think that the presence of our planet’s magnetic field was important for the development and survival of life on Earth as we currently know it.

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Like Earth, Jupiter has auroras that gleam at its poles—a result of the planet’s magnetic field interacting with energetic particles streaming from the Sun. In recent years astronomers have noticed that Ganymede and Io, two of Jupiter’s moons, each add their own personal stamp to the planet’s auroras. Pick out these planetary footprints in Jupiter’s swirling aurora on an image series from the Hubble Space Telescope in the newest Astro Bulletin, below.

Check out some of the archaeological traces in Andromeda Galaxy in the recent Astro Bulletin below.

To learn about other recent astronomical discoveries, visit the Science Bulletins website.