ADVANCES
22 Scientific American, April 2022NASA and International Space Station Archaeological ProjectARCHAEOLOGYOne Small Step
Space station archaeology digs into astronaut culture
nasa astronaut Kayla Barron floated into an International Space Station
module in January with a roll of yellow tape and an unusual assignment:
setting up the first of six “trenches” for an archaeological investigation.
Back on Earth, archaeologists Alice Gorman of Flinders University in
Australia and Justin Walsh of Chapman University in California watched
and offered feedback. They had previously mined existing video footage
to study astronaut culture, but their Sampling Quadrangle Assemblages
Research Experiment, dubbed SQuARE, marks the first real off-world “dig.”
In terrestrial archaeology, researchers often record every bone, pot-
tery fragment and stone tool found in small, well-defined trenches. Adapt-
ing that well-honed methodology, SQuARE had astronauts take daily pho-
tographs of one-meter squares marked off by tape. The re searchers back
on Earth then documented all objects entering and exiting those six spots
over 60 days, until the work wrapped up in March. “Every image is like a
layer of soil that we’re removing, revealing a new period and a new set of
activities that have happened in that area,” Walsh says. The sampled areas
included a workstation, a galley and the wall across from the U.S. toilet.
These trenches were full of artifacts, including scissors, wrenches, pens,
condiments and one of Gorman’s obsessions: Ziploc bags.
“Lots of people think of archaeology as gold masks and pyramids and
sculptures and things like that,” Gorman says—not the utensils, pots and
other objects more often studied. “That’s the really fascinating stuff.” Amid
the expensive, highly designed and irreplaceable components often found
in spacecraft, mass-produced plastic bags affixed to surfaces are crucial as
a form of what Gorman calls “portable gravity,” along with Velcro, cable
ties, handholds and footholds that help items (and people) stay in place.
Better data on such artifacts’ use could influence future space habitat
design. And SQuARE has a historic preservation component, too: the
more than 20-year-old station is set to be decommissioned in 2030. “It’s
really the direction that space archaeology should go,” says anthropologist
Beth O’Leary, a pioneer in this burgeoning field and professor emerita at
New Mexico State University, who was not involved in the study. SQuARE
data could illuminate how astronauts create subcultures in space, she adds.
In earlier work, the team showed how Russian cosmonauts over sev-
eral decades and multiple space stations informally passed down a way
of using empty wall space to create shrines honoring heroes such as astro-
naut Yuri Gagarin. “There seems to have been a transmission of what to
do,” Walsh says, “which is what culture is—it’s these traditional practices
that get developed, then reinforced and transformed.” — Megan I. GannonB I O L O G YSheathed Blades
Subtle tweaks to common genetic patterns
explain key grass leaf structurePicture a clump of grass —a spray of flat green blades that
converge into sturdy tubes near the ground. These tubes are
formed by the curled lower portion of the grass leaf, called
the sheath, which represents something of an evolutionary
triumph. It allows grass to grow from the base (instead of
the stem, like most other flowering plants) by protecting
new growth and holding mature blades upright so they can
compete for sunlight. This growth strategy helps to explain
why lawns survive mowing and how grasslands dominate
more than a quarter of Earth’s land area: by tolerating graz-
ing and wildfires better than stem-growing competitors.
Scientists have long debated the evolutionary origins
of the sheath, which is found in all grasses, including corn,
wheat and bamboo. Now a new study in Science illustrates
how the novel structure of the grass leaf arose from the
same genetic pattern that governs other plants’ leaf devel-
opment. “It’s not that we got new things bolted on and
added,” says the study’s lead author Annis Richardson,
a developmental geneticist at the University of Edinburgh.
“The connections were tweaked.”
Richardson and her colleagues started by taking 3-D
images of corn seedlings as they matured, then re-creating
the plant’s development using a computer model. The re -
search ers honed their model further by comparing it with
experimental observations, such as where certain genes
activate in plants and how genetic mutations affect leaf
shape. Then they turned to the sheath.
In the 1800s botanists proposed that the sheath part
of a grass leaf represented the evolutionary equivalent of
the petiole, the stalk that connects a typical plant’s leaf to its
stem. Later, many scientists concluded based on vein pat-
terns that beyond just the sheath, the entire grass leaf—or
most of it—actually corresponded to this stalk. Richardson
and her team tested both hypotheses in their model and
found that the older idea, linking only the sheath to the peti-
ole, offered the simplest evolutionary path and required
only subtle changes in a common genetic blueprint.
Aman Husbands, a developmental biologist at the Uni-
versity of Pennsylvania who was not involved in the study,
says the researchers tied together clues about the sheath
from other leaf studies and “put it all together into a model
that actually explains it and really settles it.”
An improved understanding of what controls leaf
shape could help scientists engineer better crops, Rich-
ardson says. Identifying the sheath’s origin also sheds
light on grass evolution. Although grass’s unique struc-
ture had enormous consequences for Earth’s landscapes
and inhabitants—including humans, who get more than
half their calories from domesticated grass grains—she
adds, “we now understand that that leaf shape wasn’t
that hard to develop.” — Julia Rosen
An archaeological “trench” in space marked by tape at the corners