Science - USA (2019-01-18)

(PHOTO) KENT LOEFFLER; GRAPHIC) KJAER

ET AL.

SCIENCE sciencemag.org 18 JANUARY 2019 • VOL 363 ISSUE 6424 241

RESEARCH

Presenting a nanosecond-

excited iron complex

Kjær et al., p. 249

Edited by Stella Hurtley

IN SCIENCE JOURNALS

IMPACT CRATERS

Impact rates on Earth

and the Moon

The rate at which impacts

produce craters on the Moon is

used to calibrate ages in plan-

etary science. Earth should also

have received similar numbers

of impacts, but many craters

have been hidden by erosion,

ice sheets, and so on. Mazrouei

et al. used infrared images of

the Moon to estimate the ages

of young lunar craters (see

the Perspective by Koeberl).

They found that the impact

rate increased within the past

~500 million years, a conclusion

strengthened by an analysis of

known impact craters on Earth.

Crater size distributions are the

same on Earth and the Moon

over this period, implying that

terrestrial erosion affects all

craters equally, regardless of

their size. —KTS

Science, this issue p. 253;

see also p. 224

PHOTOSYNTHESIS

Plugging into the pump

Photosynthetic organisms use

light to fix carbon dioxide in

a process that requires both

chemical reducing equivalents

and adenosine triphosphate

(ATP). Balancing the ratio of

these inputs is accomplished

by a short circuit in electron

flow through photosynthetic

complex I, a proton pump that

contributes to ATP produc-

tion but does not increase net

reducing equivalents in the cell.

Schuller et al. solved a cryo–

electron microscopy structure

of photosynthetic complex I

(see the Perspective by Brandt)

and went on to reconstitute

electron transfer using the elec-

tron carrier protein ferredoxin.

—MAF

Science, this issue p. 257;

see also p. 230

SOLAR CELLS

A redox road to recovery

Device longevity is a key issue

for organic-inorganic perovskite

solar cells. Encapsulation can

limit degradation arising from

reactions with oxygen and water,

but light, electric-field, and

thermal stresses can lead to

metastable elemental lead and

halide atom defects. Wang et

al. show that for the lead-iodine

system, the introduction of the

rare earth europium ion pair

Eu3+-Eu2+ can shuttle electrons

and recover lead and iodine ions

(Pb2+ and I−). Devices incorporat-

ing this redox shuttle maintained

more than 90% of their initial

power conversion efficiencies

under various aging conditions.

—PDS

Science, this issue p. 265

NEUROSCIENCE

The emotional

dimension of pain

The unpleasantness of pain is an

emotional phenomenon distinct

from pain’s sensory qualities. To

study how the brain processes

pain-related emotions, Corder

BIODIVERSITY

Ancestral history matters

B

iodiversity is sometimes quantified

purely by the number of species within

a system that allow it to function to

produce ecosystem services. Grab et

al. show that simple species counting

is too simplistic. They combined remotely

sensed land-cover analyses and crop pro-

duction records with an extensive 10-year

pollinator community survey and a com-

plete species-level phylogeny generated

using genome-wide phylogenomic methods.

They found that the equivalent of millions

of years of pollinator evolution were lost in

highly altered agricultural environments,

which decreased pollination services above

and beyond what would be expected from

a simple numerical species count. —SNV

Science, this issue p. 282

Mining bee (Andrena nasonii)

on an apple (Malus pumila) flower

osecond

plex

Published by AAAS