64 Science & technology The EconomistAugust 1st 2020
2 Dr Wetzel’s team were developing rats
as ankle supports to absorb landing shock
for parachutists when they realised that
the tethers they were working with had just
the qualities required for helmet suspen-
sions: they provide instant strong resis-
tance, which increases with impact speed.
Existing military helmets protect in situa-
tions like travel over rough terrain, colli-
sions between vehicles and with obstacles,
and being thrown around by bomb blasts.
rats offer better protection in all these
cases. Current American-army combat hel-
mets are built to withstand impact veloci-
ties of three metres a second, with newer
models being rated for just over four. Pro-
totype helmets fitted with ratsuspension
pass impact tests at five metres a second,
which Dr Wetzel says no previous helmet
suspension has achieved.
Donal McNally, a specialist in biome-
chanics at the University of Nottingham, in
Britain, says that an ideal helmet would
make the best use of the space between
shell and head, adjusting its stiffness de-
pending on the speed of impact. The rat
design does just that. However, its success
will depend on whether the shear-thicken-
ing material can be engineered to have the
correct stiffness for both slow and fast im-
pacts. Dr McNally notes also that the sus-
pension will require some clever design
because the tethers respond only to ten-
sion, not compression, making it hard to
cope with impacts from all directions.
Dr Wetzel’s priority at the moment is
getting industry to share his excitement
about the new technology. Firms selling to
civilian customers generally work faster
than people on the military side of things,
he says, and if consumer applications take
off that will generate a manufacturing and
design base which can support military
ones. To this end, his team has retrofitted
an American-football helmet with ratsus-
pension. Head protection is a huge and in-
creasing concern in gridiron football.
There has been a dramatic fall-off in the
number of youngsters taking up the sport
because of worries about head injuries. Im-
proved protection might help change that.
An independent laboratory tested the hel-
met and, in the most taxing test, found that
it reduced the “severity index” (a measure
of the likelihood of a wearer suffering brain
injury) from 393 for the helmet’s standard
version to 190. One of the laboratory’s oper-
ators said he had never seen a result of less
than 200 on the test concerned.
Nor are helmets the only possible appli-
cation for rats. Dr Wetzel and his team
have already tested them as chin straps to
hold helmets in place, and as straps for
pairs of goggles. rat-based straps could
eventually be useful for everything from
hikers’ backpacks to babies’ pushchairs.
Whether they will have applications in
ships’ ratlines remains to be seen. 7F
ar fromthe life-sustaining light of the
sun, the deep sea floor appears barren
and desolate. Its appearance, however, be-
lies a thriving bacterial ecosystem that may
contain as much as 45% of the world’s bio-
mass of microbes. This ecosystem is fu-
elled by what is known as marine snow—a
steady shower of small, nutrient-rich par-
ticles that fall like manna from the ocean
layers near the surface, where photosyn-
thesis takes place.
Not all of the snow is digestible, though.
And the indigestible parts build up, layer
upon layer, burying as they do so the bugs
in the layer below. To look at how well these
bacteria survive entombment a group of re-
searchers led by Morono Yuki of the Japan
Agency for Marine-Earth Science and Tech-
nology and Steven D’Hondt of the Universi-
ty of Rhode Island studied samples collect-
ed in 2010 by the Integrated Ocean Drilling
Programme, a decade-long international
expedition of which they were part. Their
results, just published in Nature Communi-
cations, are extraordinary. They seem to
have brought back to life bacteria that have
been dormant for over 100m years.
For many microbes, burial is an imme-
diate death sentence. Some, however, are
able to enter a state of dormancy—slowing
their metabolisms down almost, but not
quite, to zero. They can remain in this state
for considerable periods. But precisely how
long has been a subject of debate.The samples Dr Morono and Dr D’Hondt
chose for examination came from a place
in the Pacific Ocean where the sea bed is
nearly 6,000 metres below the surface.
That made drilling a challenge. But the ex-
pedition was able to recover sediment
cores stretching all the way down to the un-
derlying rock—a thickness of 100 metres in
some cases. The oldest material in these
cores dated back 101.5m years, to the mid-
dle of the Cretaceous period, the heyday, on
land, of the dinosaurs.
Examination of the sediments showed
that even the oldest still contained a few
bacteria. The question was, were these or-
ganisms dead or alive? To find out, the re-
searchers incubated the samples, slowly
feeding them compounds rich in carbon
and nitrogen in order to coax any still-liv-
ing microbes out of their dormancy.
The results shocked Dr Morono, “At first
I was sceptical, but we found that up to
99.1% of the microbes in sediment deposit-
ed 101.5m years ago were still alive.” And
there was quite a variety of them, too. The
team found representatives of phyla called
Actinobacteria, Bacteroidetes, Firmicutes
and Proteobacteria, all of which are famil-
iar to microbiologists. In one sample (ad-
mittedly from a mere 13.5m years ago) they
also discovered representatives of the ar-
chaea, a group of organisms that resemble
bacteria under a microscope, but have a
biochemistry so different that they are re-
garded as a separate domain of life.Cretaceous Park
To find such living fossils from as far back
as the Cretaceous is extraordinary. It is not
possible to be sure, given the length of time
involved, that they have undergone no
growth and cell division whatsoever. But if
they have, it will have been minimal given
the lack of nutrients in the ooze they were
found in. Nor is it likely that they migrated
there from layers above. The ooze in ques-
tion was sealed off by a bacteria-proof layer
of chert-like material called porcellanite.
This discovery will therefore throw in-
teresting light on the evolution of bacteria
on Earth. It will also raise the spirits of
those who hope to find life elsewhere in the
solar system. The sediments that will be ex-
amined for signs of biology by Persever-
ance, an American Mars rover which was
awaiting lift-off from Cape Canaveral, in
Florida, as The Economistwent to press, are
35 times older than those studied by Dr Mo-
rono and Dr D’Hondt, and have not had the
protective shielding from environmental
degradation that comes from being buried
at the bottom of the sea under many metres
of overburden. But future Mars rovers will
drill beneath the planet’s surface into strata
that have had equivalent levels of protec-
tion from rock above them, if not from sea-
water. And a factor of 35, though large, does
not sound insurmountable. 7Researchers revive bacteria that lived
at the time of the dinosaursPalaeomicrobiologyThe bugs that time
forgot
Dr Morono in his laboratory