16 | New Scientist | 31 August 2019BacteriaSpace rock Ryugu
is a dustless oddit yTHE MOST detailed pictures yet of
the asteroid Ryugu have revealed
something odd: a lack of dust.
After arriving in 2018, Japan’s
Hayabusa-2 spacecraft dropped
three landers and took a sample
from Ryugu’s surface. Now,
pictures from one of the landers
have revealed more details about
the composition of the asteroid.
Ralf Jaumann at the German
Aerospace Centre’s Institute ofCells could become
computers in bodyGENE editing can turn living cells
into minicomputers that can
record data and could track what
happens inside the body.
DNA computers have been
around since the 1990s, when
researchers created DNA able
to perform basic computer
functions. Instead of storing
information as 0s and 1s like
digital computers do, these
computers store information in
A, C, G and T, DNA’s molecular
code. One problem is that this
information doesn’t change
during a cell’s life, making DNA
computers very slow.
Now Fahim Farzadfard at
the Massachusetts Institute of
Technology and his colleagues
have created a technique that
uses DNA editing to speed up the
process. They call their system
DOMINO, for DNA-based Ordered
Memory and Iteration NetworkBiocomputing^ AsteroidsMICROORGANISMS fly into the
Atacama desert on grains of dust
carried by the wind, which may be
how they first colonised the desert.
The finding suggests that if there
are microbes on Mars, they could be
carried around the planet by global
dust storms, says Armando
Azua-Bustos at the Centre of
Astrobiology in Madrid, Spain.
The Atacama in South America
is one of Earth’s driest places, with
soils so parched they resemble
those of Mars. Some Atacama
microbes survive even in the driest
spots, but questions remain over
how they got there.
Azua-Bustos and his colleagues
suspected microorganisms arrived
on dust carried by afternoon winds
that blow in from the Pacific. To find
out, they set out Petri dishes filled
with nutrients in lines stretchingfrom the coast to the desert interior.
Any microbes flying in would land
in them. They found 28 species
growing in the dishes and extracted
DNA from several more that landed
but didn’t grow. The microbes came
from near the coast (Scientific
Reports, doi.org/c9pc).
Oceanobacillus oncorhynchi is
one of them. It lives in tidal pools.
Because the pools evaporate in the
heat of the day, it can survive being
dried out for hours – giving it a
chance of surviving the Atacama.
Azua-Bustos says such microbes
may have been the first to colonise
the desert. Mars is prone to dust
storms, so if there is any microbial
life there it could be dispersed on
dust grains. And if life can be moved
around Mars, contamination from
our probes could spread fast, he
says. ❚ Michael MarshallHow airborne microbes
conquered Mars-like desert
Planetary Science in Berlin and
his colleagues have analysed the
images. They were surprised to
see the surface of Ryugu doesn’t
have a layer of dust (Science,
DOI: 10.1126/science.aaw8627).
This is strange because dust is
expected to accumulate through
collisions in space.
One explanation could be that
fine dust becomes charged due to
solar radiation and gets removed
by electrical forces, says Jaumann.
Another is that the release of
volatile gases from the surface
might have blown the dust away.
Or maybe, if Ryugu shakes as it
travels through space, the dust
could have gradually settled in the
interior of the asteroid, meaning
we can’t see it.
The pictures also revealed
details of rock texture on the
surface. The images show there
are two kinds of rock on Ryugu’s
outer layer, dark and rough or
bright and smooth, and they
both take up an equal share
of the surface. ❚ Abigail BeallOperator. It is designed to
respond to various biological
cues, such as small molecules
or light, and builds on CRISPR
gene-editing techniques.
Current technologies used to
edit genes in cells or organisms
are limited. Their capacity to
store data stops after one or two
molecular events. In contrast,
DOMINO can be programmed to
edit DNA after complicated chains
of events, allowing it to encode
more information quickly.
One application for the
system could be to monitor
sugars, by programming it to
respond to lactose for example.
When a bacteria with the system
encounters lactose, DOMINO
would make changes to its DNA
(Molecular Cell, doi.org/c9n3).
The history of events are then
stamped onto the DNA in the form
of unique mutational signatures
that don’t fade over time even
after the cues, in this case lactose,
fade away, says Farzadfard. ❚
Ruby Prosser ScullyAP
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