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62

63

January/February 2018^ DISCOVER^65

CLOCKWISE FROM BOTTOM LEFT: ISRO/ISSDC/KEVIN M. GILL/CC BY 2.0; MAX PLANCK INSTITUTE FOR NUCLEAR PHYSICS (2)

Ice Storms

on Mars

❯

A NEW WEATHER SIMULATION predicts nighttime

snow flurries on arid Mars, shedding light on

how the Red Planet’s scarce water supplies move

through the atmosphere.

In 2008, the Phoenix lander observed snowfall in Mars’ sky.

But scientists believed the snow, falling under its own slight

weight, would take hours to drift down, and would probably

evaporate before hitting the ground.

The new research, published in August in Nature

Geoscience, shows nighttime air currents are turbulent, with

convection strong enough to churn the snow down in a

matter of minutes, resulting in more reaching the ground.

While the amount of snow is minimal, that precipitation

would be a crucial step in Mars’ water cycle, both

present and past.

Lead author and planetary scientist Aymeric Spiga at the

Université Pierre et Marie Curie in Paris says that the snow

in his model is more like an ice storm of tiny particles than

Earth’s intricate, fluffy flakes. Standing on Mars early in

the morning, “you would see it as a very thin and sparse

frost,” he says. — KOREY HAYNES

Positive Proton

Loses Weight

❯

THE PROTON GOT a little lighter

this year, thanks to measurements

of its mass that are three times

more precise than the best previous effort.

This tweak to one of the building blocks

of matter, good to 32 parts per trillion,

should help refine measurements of

other phenomena and test fundamental

symmetries in nature.

To reweigh the proton, scientists in

Germany trapped the particle within

magnetic and electric fields. Using

phenomenally sensitive detectors from

Japan, they compared the particle’s

vibrations, which are related to its mass,

with the vibrations of a carbon atom (the

mass standard-bearer for atoms).

Students everywhere hope they don’t

have to memorize the mass calculated by

the researchers and published in July in

Physical Review Letters: 1.007276466583

atomic mass units. — DEVIN POWELL

Physicists set up a Penning Trap, which

manipulates electric and magnetic fields,

to study a single proton in isolation. They

found its mass was actually a little lower

than was previously estimated.

While astronomers

knew Mars was home

to the occasional light

snowfall, they recently

learned the Red Planet

may also host more

intense precipitation.