The New York Times - 06.08.2019

D2 N THE NEW YORK TIMES, TUESDAY, AUGUST 6, 2019

Sail on, pushed by the wind of

sunlight.

Engineers have recently dem-

onstrated how they can steer

LightSail-2, a small privately

financed spacecraft with a billow-

ing silver sail. The technology

could be used to propel future

space probes through the solar

system.

Most space missions today are

propelled by engines that provide

bursts of acceleration with limited

amounts of fuel.

The rest of the time, the space-

craft are coasting.

By contrast, with LightSail-2,

particles of light from the sun

bounce against the spacecraft’s

344 square feet of sails — roughly

the area of a boxing ring — gener-

ating a modicum of force, the

equivalent of the weight of a

paper clip pushing down on your

hand. But because the sun always

shines, the sail offers a contin-

uous nudge that builds up over

time to faster speeds — all with-

out needing any fuel at all.

The achievement was an-

nounced by officials at the non-

profit Planetary Society.

KENNETH CHANG

HIGH FLIERS

Spacecraft Shows

Solar Sailing’s

Potential in Space

PLANETARY SOCIETY, VIA ASSOCIATED PRESS

Observatory

FINDINGS, EVENTS AND MORE

It’s a myth that black widow female spiders always kill

and consume their mates. But courtship remains per-

ilous for males, cannibalism or no. The terrain, navi-

gated in the dark, is challenging. The female’s web

releases come-hither pheromones, but only about 12

percent of prospective males manage to reach one.

Once there, they can expect to encounter male rivals.

Usually, this results in wild displays of machismo.

The males (the smaller one at right, above) slash the

female’s webs to make them less enticing to others.

They deposit “mating plugs” in the female’s body to

block rival sperm.

Why not simply avoid the competition and seek

out females’ webs empty of other males? But male

black widows actually seem to thrive on the competi-

tion, according to a new study. Researchers found

that male black widows find potential mates faster by

following the silk trails left behind by other males.

“Males have to race to find females,” said Cather-

ine Scott, an arachnologist in Canada and the study’s

lead author. “It makes sense for them to try to use all

the tricks they can to find females as soon as possible,

even if there are other males that have already found

her.” KNVUL SHEIKH

WEB DATING

How Does a Male Black Widow Find a Mate? Follow the Other Guys

SEAN McCANN

Today, Mars is a cold, dry world,

home to dust devils and robotic

explorers. But many scientists

suspect it was once waterlogged.

A new study suggests that a

75-mile-wide impact scar in the

Martian northern lowlands is to

the red planet what the Chicxu-

lub crater is to Earth: the mark of

a meteor that generated a mega-

tsunami when the planet was

relatively young. If accurate, the

finding adds evidence to the

hypothesis that Mars once had an

ocean, and would have implica-

tions for our search for life there.

Whether Mars was ever warm

and wet enough to retain a liquid

water ocean has long been debat-

ed.ROBIN GEORGE ANDREWS

RED PLANET RESEARCH

Finding Ground Zero

For a Martian Tsunami

JPL/NASA

Late blight is a common disease

of plants such as tomatoes and

potatoes, capable of wiping out

entire crops on commercial-scale

fields. Caused by a fungus-like

pathogen, it first appears as black

or brown lesions on leaves, stems,

fruit or tubers. If conditions are

favorable, it can quickly spread to

other plants through wet soil and

as wind-scattered spores.

In the mid-19th century, late

blight famously caused the Irish

potato famine. Today it still

causes more than 6.7 billion dol-

lars in annual losses worldwide.

Small farms and organic growers

are often the hardest hit, because

they have fewer resources to

identify and treat the disease.

But farmers may have a new

weapon in the arsenal. The tech-

nology, designed by North Car-

olina State University re-

searchers, relies on the science of

subtle plant odors, and it can

recognize sick plants by using a

simple test strip that plugs into a

reader on a smartphone.

Plants emit signaling chemicals

from their leaves, not unlike the

pheromones released by humans.

“If a plant is diseased, the type

and concentration of these vola-

tile organic compounds changes,”

said Qingshan Wei, a biomolecu-

lar engineer at North Carolina

State. By sampling a plant’s emis-

sion profile, a farmer can assess

whether or not a sample of their

crop is infected, Dr. Wei said.

KNVUL SHEIKH

POSTMODERN AGRICULTURE

Farmers May Turn

To Smartphones

To Fight Crop Diseases

ZHENG LI

‘Jakarta keeps sinking. If subsidence

continues at the same rate, 95 percent of

northern Jakarta will be underwater by

2050.’

Heri Andreas, of the Bandung Institute of Technology in Indonesia,
who predicts that one-third of the nation’s capital will be underwater by
the middle of the century.

In June 2013, in a parking lot in

Wilsonville, Ore., an estimated

50,000 bumblebees dropped dead.

Piles of carcasses scattered be-

neath dozens of linden trees

signified the largest mass bee kill

ever recorded.

Oregon determined that a

pesticide used against aphids had

poisoned the bees. But more

reports surfaced of mass bumble-

bee deaths around Oregon. Ex-

plaining them wasn’t as simple.

“Not every dead bee could be

because of a pesticide,” said Su-

jaya Rao, an entomologist who

studied the bee deaths. “There

are strange phenomena in nature

that lead to things like this.”

In a new study, Dr. Rao and

other researchers proposed an

explanation: If it’s too cold, and

the bees are too weak, and the

trees are enticing but don’t

produce enough nectar — all that

may tip bumblebees over the

edge. “Not all bee death is related

to humans,” said Claire Lande,

the study’s co-author. “Sometimes

it just happens.”JOANNA KLEIN

AN INSECT INVESTIGATION

Multiple Suspects

Sought in Bee Deaths

CLAIRE LANDE

Daily nuggets of science for mobile readers: nytimes.com/trilobites

ONLINE:TRILOBITES