[meteorite-list] At Pluto, New Horizons Finds Geology of All Ages, Possible Ice Volcanoes, Insight into Planetary Origins

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 9 Nov 2015 15:27:55 -0800 (PST)
Message-ID: <201511092327.tA9NRt2t027110_at_zagami.jpl.nasa.gov>

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151109

At Pluto, New Horizons Finds Geology of All Ages, Possible Ice Volcanoes,
Insight into Planetary Origins

November 9, 2015

[Image]
Scientists using New Horizons images of Pluto's surface to make 3-D
topographic maps have discovered that two of Pluto's mountains,
informally named Wright Mons and Piccard Mons, could possibly be ice
volcanoes. The color is shown to depict changes in elevation, with blue
indicating lower terrain and brown showing higher elevation; green
terrains are at intermediate heights.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

[Image]
The informally named feature Wright Mons, located south of Sputnik
Planum on Pluto, is an unusual feature that's about 100 miles (160
kilometers) wide and 13,000 feet (4 kilometers) high. It displays a
summit depression (visible in the center of the image) that's
approximately 35 miles (56 kilometers) across, with a distinctive
hummocky texture on its sides. The rim of the summit depression also
shows concentric fracturing. New Horizons scientists believe that this
mountain and another, Piccard Mons, could have been formed by the
'cryovolcanic' eruption of ices from beneath Pluto's surface.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

>From possible ice volcanoes to geologically diverse surfaces to oddly
behaving moons that could have formed through mergers of smaller moons,
Pluto system discoveries continue to surprise scientists on NASA's New
Horizons mission team.

"The New Horizons mission has taken what we thought we knew about Pluto
and turned it upside down," said Jim Green, director of planetary
science at NASA Headquarters in Washington. "It's why we explore - to
satisfy our innate curiosity and answer deeper questions about how we
got here and what lies beyond the next horizon."

Press Conference Graphics

View the graphics from the Nov. 9 New Horizons media briefing at the
2015 AAS Division for Planetary Sciences Meeting.
<Press-Conferences/November-9-2015.php>

The New Horizons team is discussing numerous findings at the 47th Annual
Meeting of the Division for Planetary Sciences (DPS) of the American
Astronomical Society (AAS) this week in National Harbor, Maryland. Just
four months after the spacecraft encountered Pluto, science team members
are presenting more than 50 reports on exciting discoveries.

"It's hard to imagine how rapidly our view of Pluto and its moons are
evolving as new data stream in each week. As the discoveries pour in
from those data, Pluto is becoming a star of the solar system," said
mission Principal Investigator Alan Stern of the Southwest Research
Institute, Boulder, Colorado. "Moreover, I'd wager that for most
planetary scientists, any one or two of our latest major findings on one
world would be considered astounding. To have them all is simply
incredible."

In one such discovery, New Horizons geologists have combined images of
Pluto's surface to make 3-D maps that indicate that two of Pluto's
most distinctive mountains could be cryovolcanoes - ice volcanoes that may
have been active in the recent geological past.

The two cryovolcano candidates are large features measuring tens of
miles (tens of kilometers) across and several miles or kilometers high.
"These are big mountains with a large hole in their summit, and on Earth
that generally means one thing - a volcano," said Oliver White, New
Horizons postdoctoral researcher with NASA's Ames Research Center,
Moffett Field, California. While their appearance is similar to
volcanoes on Earth that spew molten rock, ice volcanoes on Pluto are
expected to emit a somewhat melted slurry of substances such as water
ice, nitrogen, ammonia, or methane on Pluto.

White stresses that the team's interpretation of these features as
volcanoes is tentative. However, "If they are volcanic, then the summit
depression would likely have formed via collapse as material is erupted
from underneath. The strange hummocky texture of the mountain flanks may
represent volcanic flows of some sort that have travelled down from the
summit region and onto the plains beyond, but why they are hummocky, and
what they are made of, we don't yet know."

If Pluto is proven to have volcanoes, it will provide an important new
clue to its geologic and atmospheric evolution. "After all, nothing
like this has been seen in the deep outer solar system," said Jeffrey Moore,
New Horizons Geology, Geophysics and Imaging team leader, also from NASA
Ames.

Pluto's Long History of Geologic Activity

Another of the more surprising findings from New Horizons is the wide
range of surface ages found on Pluto, from ancient to intermediate to
relatively young in geological terms. Crater counts used to determine
surface unit ages indicate that Pluto has ancient surface areas dating
to just after the formation of the planets, about 4 billion years ago.
In addition, there's a vast area that was geologically born "yesterday,"
meaning it may have formed within the past 10 million years. This area
- informally named Sputnik Planum - appears on the left side of Pluto's
"heart" and is completely impact-free in all images returned to date.

Scientists wondered if Sputnik Planum's smooth, icy plains were an
oddity; did a recent geological episode form the plains long after all
other geologic activity ceased?

[Image]
Locations of more than 1,000 craters mapped on Pluto by NASA's New
Horizons mission indicate a wide range of surface ages, which likely
means that Pluto has been geologically active throughout its history.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

Apparently not. New data from crater counts reveal the presence of
intermediate or "middle-aged" terrains on Pluto as well. This suggests
that Sputnik Planum is not an anomaly - that Pluto has been geologically
active throughout much of its more than 4-billion-year history. "We've
mapped more than a thousand craters, which vary greatly in size and
appearance," said postdoctoral researcher Kelsi Singer, of the Southwest
Research Institute (SwRI) in Boulder, Colorado. "Among other things,
I expect cratering studies like these to give us important new insights
into how this part of the solar system formed."

Building Blocks of the Solar System

Crater counts are giving the New Horizons team insight into the
structure of the Kuiper Belt itself. The dearth of smaller craters
across Pluto and its large moon Charon indicate that the Kuiper Belt
likely had fewer smaller objects than some models had predicted. This
leads New Horizons scientists to doubt a longstanding model that all
Kuiper Belt objects formed by accumulating much smaller objects of less
than a mile wide. The absence of small craters on Pluto and Charon
support other models theorizing that Kuiper Belt objects tens of miles
across may have formed directly, at their current - or close to
current - size.

In fact, the evidence that many Kuiper Belt objects could have been
"born large" has scientists excited that New Horizons' next potential
target - the 30-mile-wide (40-50 kilometer wide) KBO named 2014 MU69 -
which may offer the first detailed look at just such a pristine, ancient
building block of the solar system.

[Animation]
Most inner moons in the solar system keep one face pointed toward their
central planet; this animation shows that certainly isn't the case with
the small moons of Pluto, which behave like spinning tops. Pluto is
shown at center with, in order, from smaller to wider orbit: Charon,
Styx, Nix, Kerberos and Hydra.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

Spinning, Merged Moons

The New Horizons mission is also shedding new light on Pluto's
fascinating system of moons and their unusual properties. For example,
nearly every other moon in the solar system, including Earth's moon,
is in synchronous rotation, but not so of Pluto's small moons. These small
satellites are spinning much faster, with Hydra - the most distant moon
- rotating an unprecedented 89 times during a single lap around Pluto.
Scientists believe these spin rates could be chaotic (i.e., variable)
because Charon exerts a strong torque that prevents each small moon from
settling down into synchronous rotation, which means keeping one face
toward the planet.

Another oddity of Pluto's moons: scientists expected the satellites
to wobble, but not to this degree. "Pluto's moons are behaving like
spinning tops," said co-investigator Mark Showalter of the SETI
Institute in Mountain View, California.

Images of Pluto's four smallest satellites also indicate that several
of them could have been born from mergers of two or more former moons,
suggesting the presence of more moons at some point. "We suspect from
this that Pluto had more moons in the past, in the aftermath of the big
impact that also created Charon," said Showalter.

[Image]
New Horizons data indicates that at least two (and possibly all four)
of Pluto's small moons may be the result of mergers between still smaller
moons. If this discovery is borne out with further analysis, it could
provide important new clues to the formation of the Pluto system.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

Pluto's Frigid, Extended Atmosphere

The New Horizons team is presenting new data at DPS that reveal Pluto's
upper atmosphere is significantly colder and therefore more compact than
Earth-based models had indicated. As a result, scientists have
discovered that Pluto's atmospheric escape rate is thousands of times
lower than had been thought. It now appears that Pluto's atmosphere
escapes by the same mechanism as do gases from the atmospheres of Earth
and Mars - rather than the previously believed escape process that more
resembled escape from cometary atmospheres.

New Horizons is part of NASA's New Frontiers Program, managed by the
agency's Marshall Space Flight Center in Huntsville, Alabama. The Johns
Hopkins University Applied Physics Laboratory in Laurel, Maryland,
designed, built, and operates the New Horizons spacecraft and manages
the mission for NASA's Science Mission Directorate. The Southwest
Research Institute leads the science mission, payload operations, and
encounter science planning.

For more information on the New Horizons mission, including fact sheets,
video and images, visit *http://www.nasa.gov/newhorizons** and
**http://pluto.jhuapl.edu*.

Media contacts:

Dwayne Brown / Laurie Cantillo
Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown at nasa.gov <mailto:dwayne.c.brown at nasa.gov> /
laura.l.cantillo at nasa.gov <mailto:laura.l.cantillo at nasa.gov>

Mike Buckley
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-7536
michael.buckley at jhuapl.edu <mailto:michael.buckley at jhuapl.edu>

Maria Stothoff
Southwest Research Institute, San Antonio
210-522-3305
maria.stothoff at swri.org <mailto:maria.stothoff at swri.org>
 
Received on Mon 09 Nov 2015 06:27:55 PM PST