Water’s role in mantle movement thrown into doubt

Water may not control the flow of rocks in Earth’s interior as much as researchers had thought.


Convection in the Earth’s mantle (orange ring around the yellow outer core) may not depend on water’s presence for a lubricating effect, contrary to what geophysicists have assumed.

For decades, scientists have believed that the presence of water in deep-Earth rock makes it less viscous and allows it to flow. That movement underpins all sorts of geophysical phenomena, from the jostling of tectonic plates to giant convection patterns that transfer heat within Earth’s mantle. It also helps control the planet’s cycling of carbon and other life-critical elements from the deep interior toward the surface and back.

But high-pressure experiments on crystals of olivine, a common mineral in the mantle, hint that the textbook explanation may be at least partly wrong. Hongzhan Fei, a geochemist at the University of Bayreuth in Germany, and his colleagues describe the findings today in Nature.

Many laboratory experiments have demonstrated water’s weakening effect on minerals. But most of those studies looked at multiple crystals that were oversaturated with water, says Fei. When the crystals were squeezed, water between the grains could have allowed them to slide along their boundaries rather than causing deformation inside the crystals, as would be expected with true rock flow. Read more

How to boil water without bubbles

One trick to test whether a frying pan is hot enough is to sprinkle water on it. If the surface is sufficiently above the boiling point of water, droplets will skip across the pan. Those jittery beads of water are held up from the hot pan by a cushion of steam. The vapour cushion collapses as the surface falls below the ‘Leidenfrost temperature’, causing furious bubbling and spitting when the water droplet hits the surface and boils explosively.

001The Leidenfrost effect lies behind the discovery, published today in Nature1, that water can be made to boil without any bubbling if a surface is specially treated so that the vapour cushion does not break down. The key is to make the surface very water-repellent, according to Ivan Vakarelski, an engineer at the Clean Combustion Research Center at the King Abdullah University of Science and Technology in Thuwal, Saudi Arabia, and his colleagues. The effect might be used to carefully control how metals are cooled and heated, or to reduce drag on ships. Read more

Troubled waters

The easiest way to create a nature reserve from a car park is simply to declare it as such. The land is then designated as protected, and counts towards the relevant government’s targets to set aside a certain amount of its territory from development. That is a ridiculous example, of course, and would never happen on land — so why do we allow a similar exercise to happen in the sea?

troubled-watersNo one should doubt that our seas need protection. Overfishing, pollution and climate change are fundamentally changing some of the most important regions on the planet. And the conservation response — marine protected areas (MPAs) — should be a key tool to safeguard the world’s maritime environment. By setting aside areas in which human activity is tightly regulated, the thinking goes, governments can ensure that key habitats and species are preserved. Read more

Tableau waters your plants as nature intended

Many of us like to have houseplants in our homes, bringing a little of the outside inside. The problem is remembering to water them on a regular basis. Tableau is a new take on an automatic watering system for houseplants that aims to make it easy to avoid either over- or under watering these fussy lodgers.

10Dutch design start-up Pikaplant based the Tableau irrigation system based on nature’s own method for keeping plants healthy and happy. In contrast to other “self-watering” products we’ve seen, it attempts to mimic the wet-dry cycle in which the roots of a plant absorb water for a period of time before drying out once again. Ad infinitum. Read more

Marine biology network launches into choppy waters

Ambitious European project hopes to navigate uncertain funding future.


The sea squirt could become a top model organism at Europe’s new marine biology centre.

Sometimes good ideas take a while to be picked up. In 1872, Anton Dohrn, a pioneering German biologist, wrote a commentary in Nature proposing the foundation of “a net of scientific stations” along European coasts, focusing on marine biology (A. Dohrn Nature 5, 277–280; 1872 ). Almost 140 years later, an institute that bears Dohrn’s name is leading a twenty-first-century realization of his idea.

The European Marine Biological Resource Centre (EMBRC) will launch this week at a meeting in Naples, Italy, with the Anton Dohrn Zoological Station in Naples (SZN) taking the lead. Linking 15 existing research centres in 8 countries (see ‘Marine network’), the project will create an overarching organization for European research on marine biology, and provide model organisms for studying fundamental molecular biology and for screening drug candidates, for example. But the project has yet to secure the ambitious budget needed to realize its full potential. Read more