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| © Photo: USGS, HVO Aerial view of the ocean entry zone where lava erupting from Kilauea’s Lower East Rift Zone poured into the sea earlier this year. |
By Maddie Stone, Gizmodo
Kilauea’s historically huge 2018 eruption
didn’t just transform the southeastern corner of Hawaii’s Big Island.
Most of the lava wound up spilling into the ocean, creating an enormous
new undersea delta that hardy ocean microbes are already colonizing.
That finding, along with the broader exploratory campaign that made
it possible, might inform the search for life on an icy moon of Saturn.
That’s
according to Woods Hole Oceanographic Institution (WHOI) geochemist
scientist Chris German, who presented the unpublished findings along
with WHOI volcanologist Adam Soule at the American Geophysical Union
conference earlier this month. These scientists had a rare opportunity
to map and explore Hawaii’s southeastern coastline in late August and
early September—shortly after Kilauea’s eruption had ceased—using the
research vessel E/V Nautilus and the remotely operated vehicle Hercules.
The reason the research vessel was in the neighborhood? To study the Lō`ihi seamount,
an undersea volcano just south of the Big Island that, according to
German, is one of Earth’s best comparisons to potential hydrothermal
systems on the seafloor of Enceladus, an ice-crusted moon in Saturn’s
E-ring with a liquid water ocean beneath its surface.
As
German explained to Gizmodo, most of the hydrothermal systems humans
have studied so far occur at mid-ocean ridges, where tectonic plates are
spreading apart and causing hot magma from the mantle to burble up near
the surface. The mineral-rich fluids spewing out of these so-called
black smokers can get as hot as 400 degrees Celsius,
which German says is far hotter than any hydrothermal system we’re
likely to find on Enceladus. The depth of many black smokers means that
life around them is subjected to crushing pressures that alien microbes
on a gravitationally puny moon would have no experience with, either.
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| © Image: Adam Soule Location of the 2018 lava flows from Kilauea’s eruption, which deposited twice as much material in the ocean as it did on land. |
Lō`ihi is different. A “hotspot” volcano in the middle of the Pacific
tectonic plate, it emits cooler hydrothermal fluids at shallower depths
(and therefore lower pressures). It’s an environment not unlike
something we could imagine existing on a wee ocean world orbiting
Saturn.
German, along with Darlene Lim at the NASA Ames Research
Center and others, recently received funding from NASA and the National
Oceanic Atmospheric Administration (NOAA) to pursue that idea as part of a new astrobiology research program called SUBSEA.
In August, the researchers shipped off for a multi-week expedition to
map the seamount, collect geochemical and microbiological samples, and
test space exploration protocols.
But they wound up getting a
little extra bang for their buck when German and Soule realized the
mission’s timing—right as Kilauea was erupting—offered a rare
opportunity to see how another ocean environment was being transformed
by a different volcano. Soule worked with NOAA and the National Science
Foundation to acquire funding to divert E/V Nautilus from Lō`ihi for a
day to scope out the seafloor along Kilauea’s south flank, including the
lava’s 3-mile-wide ocean entry site.
Using E/V Nautilus’ sonar
system, the researchers first set about mapping the seafloor. They
discovered a gigantic pile of freshly cooled lava that stretched some
1.5 kilometers offshore and sloped steeply down to a depth of about
1,000 meters. Comparing this new information with maps produced in 2006,
the researchers estimate that nearly 800 million cubic meters of
lava—two thirds of what erupted—wound up offshore.
“Just seeing
where [the lava] was and how much of it there was was a huge benefit for
understanding the eruption,” Soule told Gizmodo.
A few weeks
later, on September 11, after the researchers had already completed nine
dives on Lō`ihi with the ROV Hercules, they decided to send the robotic
probe over to the new lava delta for a closer look. To the team’s
surprise, on a lava flow at a depth of about 650 meters, they discovered
gooey, bright yellow mats. Some kind of microbial growth had already up
taken up residence on the lava flows, apparently drawn to hydrothermal
fluids escaping the fresh rock.
Samples of those bugs are still
being analyzed in the lab, but German said it wouldn’t be entirely
surprising if whatever colonized the area there is at least related to
the bright yellow microbes found around Lō`ihi, whose colors indicate
they use iron or sulfur as an energy source.
German stressed that
it’s the Lō`ihi seamount that’s the more relevant environment for
imagining life on Enceladus. But it’s interesting to think that whatever
lives there might have quickly set up shop on Kilauea’s new digs. And
if further analysis demonstrates that to be the case, it could be
relevant to future planetary exploration missions.
Warning that he
was veering into the realm of speculation, German wondered if the bugs
that thrive in Lō`ihi’s hydrothermal fluids are sloshing around the
ocean at low levels, allowing some colonizers to easily latch on to
fresh real estate around Kilauea as soon as it became available.
“If
that can happen [on Earth], maybe I don’t have to worry about how to
build a robot that can dive,” to Enceladus’ seafloor, German said.
“Maybe I can just probe the water near the surface” for life.
Bill
Chadwick, a marine geologist at Oregon State University who wasn’t
involved with the new research, called the seafloor mapping endeavor
“very cool,” noting that this is probably one of the first times a
land-based volcano’s undersea lava deposits had been explored so soon
after an eruption. He wasn’t surprised to learn that microbes had
already begun colonizing the environment, noting that this has been
observed “many times” at Axial Seamount off the coast of Oregon.
“Obviously,
the Kilauea case is a bit different since the lava was erupted on land
and then flowed into the ocean,” he wrote in an email. “So presumably
the microbes were in the ocean already and are colonizing the sites
where hydrothermal circulation is happening on the cooling lava flows.”
Clearly,
much more research is needed to understand the critters living around
Hawaii’s hydrothermal systems, to say nothing of whether there’s life on
Enceladus. Both German and Soule expressed interest in going back to
Kilauea’s lava delta again, perhaps as soon as next year, to see how the
environment is changing over time.
As German put it, “We have a brand new natural laboratory on the seafloor to study. And we know when it turned on.”
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