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.

Check out the Science Bulletins website to discover more new astronomy research.

The rock that paves Mars's vast Arabia Terra region is very ancient and cratered. Now, the powerful HiRISE camera on the Mars Reconnaissance Orbiter has taken striking images of wind-eroded outcrops on some of the crater floors. The outcrops' sedimentary layers appear to have built up with rhythmic regularity, suggesting that random, catastrophic events such as floods or volcanic eruptions did not create them.

So what did? HiRISE's high-resolution images allowed Mars researchers to use investigative techniques practiced by Earth geologists. A team of scientists from the California Institute of Technology, the U.S. Geological Survey, and the University of Arizona reconstructed a 3D topographic map of a hilly region in Arabia Terra. They used this map to measure the height and pattern of the rock layers.

The results suggest that regular climate events built up the layers in stages. The best candidate for what would set off such cycles is the shift of Mars's tilt on its axis, which varies by a few degrees on a 100,000-year rhythm. These types of orbital changes on Earth induce periodic ice ages due to the planet's position relative to the Sun.

See more of HiRISE's images—including a movie of the 3-D map—in the latest AMNH Astro Bulletin.