4 October 2014 | NewScientist | 15

FRACKING wasn’t invented by humans. The method of using pressurised fluids to break apart rocks was around at least 700 million years ago, and explains one of the world’s strangest rock formations.

The Tava sandstone has baffled scientists for over a century. Found in the Front Range of the Rocky mountains in Colorado, it appears to have defied the rules

of geology. The rock formed by sandstone being injected as a liquid into surrounding layers of granite. While igneous rocks start life as a liquid, sandstone forms by sedimentation and will usually bend or break under stress rather than liquefy.

Christine Siddoway at Colorado College in Colorado Springs and her colleagues suggest that between 660 and 800 million

years ago, a nearby fault blasted the region with a series of enormous earthquakes. When quakes strike loose, wet sediment, the material begins to behave like a liquid, Siddoway says (Lithosphere, doi.org/v3h).

Huge slabs of rock shearing off from the fault could have hit the sediments below with enough force to drive them into solid granite, in a natural fracking event. “These are really extraordinary rocks,” says Siddoway.

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Immune response predicts recovery time after surgery

THE operating room is booked, the surgeon is ready – but is your body? One day a blood test will help predict whether you’ll need days or weeks to recover from surgery.

An operation is a stressful experience for your body. The trauma of the knife floods the blood with immune molecules that can trigger inflammation. As a result, some people are confined to bed for weeks, while others can be on their feet within days. The difference probably lies in individual variations in the immune response.

To find out more, a team at Stanford School of Medicine in California, led by Brice Gaudillière, used a cell-mapping

technique called mass cytometry to search for an “immune signature” that predicts recovery times. Mass cytometry allows researchers to work out which immune cells are present in a blood sample, and what molecules they are producing – a measure of their activity.

They analysed samples from 32 people who’d had hip-replacement surgery, taking samples at various times in the following six weeks. If a particular type of white blood cell was active in the first 24 hours after surgery, the person was more likely to take at least three weeks to recover. If the activity of these cells was low or decreased in the first 24 hours, they recovered faster (Science Translational Medicine, doi.org/v2p).

Gaudillière is now looking to develop a blood test that predicts recovery times before surgery is carried out.

Ancient quake fracked mystery rock

Earth gets a new companion

ADD one to the entourage. Newly discovered asteroid 2014 OL339 is the latest quasi-satellite of Earth.

The asteroid, which is between 90 and 200 metres in diameter, has been hanging out near Earth for about 775 years. It will move on in about 165 years, say Carlos and Raul de la Fuente Marcos at the Complutense University of Madrid in Spain, who have just described it (arxiv.org/abs/1409.5588v1).

Quasi-satellites orbit the sun but are close enough to Earth to look like companions. Earth’s gravity has guided 2014 OL339 into an eccentric wobble, which causes the rock to appear to circle backwards around the planet.

With four quasi-satellites catalogued so far, Earth comes in second to Jupiter’s six, though the gas giant probably has many more that we can’t see. The same is likely true of Earth, as small space rocks are notoriously hard to find.

Tap, tap, tap... is this molecule on?

THE world’s smallest microphone, made from a single molecule, is listening.

Smaller microphones can detect smaller vibrations. Yuxi Tian of Lund University in Sweden and his colleagues have taken this idea to extremes by embedding a molecule of dibenzoterrylene inside a crystal. When sound waves disturb the molecule, it vibrates, shifting the frequencies of light it absorbs. So by shining a laser into the crystal and watching for changes in absorption frequencies, the team can listen in on the sound it picks up (Physical Review Letters, doi.org/v3d).

The team hope the device could be used as an acoustic microscope to spot tiny motions in chemical and biological systems.

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