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Columns of compact snow called Nieve penitente with moon

Icy spikes called penitentes — seen here in Chile — might also form on Jupiter’s moon Europa. Credit: Art Wolfe/Getty

Planetary science

Spacecraft beware: huge spines of ice might guard a glimmering moon

Touchdowns on Jupiter’s moon Europa, which might host life, could be risky.

The Jovian moon Europa might bristle with 15-metre-tall ice blades around its equator, posing a formidable hazard for future missions to the surface.

Images of Europa, which probably harbours a saltwater ocean, have led scientists to think that a lander could touch down on the moon’s icy, seemingly smooth surface. But a team led by Daniel Hobley at Cardiff University, UK, suspected that the surface ice could sublimate, or change from a solid to a gas without melting, to form spine-like structures called penitentes.

These spikes form on Earth when a steady stream of sunlight repeatedly reflects back and forth inside small pits in cold, dry snow. The sunlight’s heat causes snow from the pits’ edges and bottoms to sublimate. The pits grow wider and deeper until only their edges remain, as tall blades of ice.

The team used surface temperature and reflectivity data to estimate sublimation rates across Europa. The results suggest that conditions at Europa’s equator could spur the formation of massive penitentes spaced 7.5 metres apart.

More Research Highlights...

Light micrograph of a human egg cell during fertilisation

As a human egg cell is fertilized, two chromosome-containing cellular structures (dotted circles, centre) merge into one — a process that often goes wrong. Credit: Pascal Goetgheluck/Science Photo Library

Developmental biology

The error-prone step at the heart of making an embryo

High-resolution imaging shows why the union between two sets of chromosomes goes awry as least as often as not.
Satellite image of broken iceberg B-44.

Dark water borders chunks of iceberg broken off a West Antarctica glacier. The melting of the region’s ice sheet could allow the bedrock to rise, sloughing water into the ocean. Credit: NASA

Climate change

Antarctic rocks on the rebound could raise sea level much more than expected

When the ice covering the west of the continent disappears, the bedrock could rise up and shove extra water into the ocean.
Monteverde Cloud Forest Preserve, Costa Rica

Mist wafts through the trees at the Monteverde Cloud Forest Biological Preserve in Costa Rica. Cloud forests around the world are threatened by development, wood collection and climate change. Credit: Stefano Paterna/Alamy

Conservation biology

Forests that float in the clouds are drifting away

Tropical cloud forests are safe havens for a vast range of creatures and plants, but they are under siege around the globe.
Illustration of a brown dwarf

A rapidly spinning brown dwarf (pictured, artist’s impression) tends to have narrow atmospheric bands; the faster the spin, the thinner the bands. Credit: NASA/JPL-Caltech

Astronomy and astrophysics

Dim stars that have failed at fusion are masters of spin

Three brown dwarfs whirl on their axes at a dizzying rate that might be close to the celestial speed limit for these bodies.
Aerial photograph of beef cattle standing at the Texana Feeders feedlot in Floresville, Texas

Large-scale facilities such as this feedlot in Floresville, Texas, help to meet the global appetite for beef and other red meat, which remains strong despite the growing consumption of chicken and fish. Credit: Daniel Acker/Bloomberg/Getty

Agriculture

Meat lovers worldwide pay climate little heed

People are eating more poultry and fish — but they’re not giving up their hamburgers.
Midshipmen at dining table eat in formation, CIRCA 1900

Midshipmen in the United States in around 1900. A study found that body-mass index, a gauge of obesity, has increased with the generations during the twentieth century. Credit: Buyenlarge/Getty

Metabolism

A century of US data documents obesity’s racially skewed rise

An analysis also finds that obesity is common at a much younger age among people born in the early 1980s than those born in the late 1950s.
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