Five
years ago this month, on July 14, 2015, the New Horizons spacecraft made its
historic flyby of Pluto, revealing a beautiful, complex planet and changing our
view and understanding of that planet forever.
It
is incredibly hard to believe that half a decade has passed since that amazing
time, when Pluto became a rock star and made headlines around the world.
So
many expected to find an inactive, dead world and were that much more surprised
when instead, the spacecraft and its science instruments revealed a planet more
geologically active than Mars, a planet with floating glaciers, windswept
dunes, cryo-volcanoes, layers of atmospheric hazes, bladed terrains, mountains
of water ice, interaction between surface and atmosphere, a likely subsurface
ocean, and more than anything else, an iconic heart-shaped feature named
Tombaugh Regio.
In
the five years that have passed since then, numerous scientific papers have
been written based on the data New Horizons returned. While it flew on past a
second target and then proceeded to do more science studying the Kuiper Belt,
planetary scientists, recognizing the flyby raised many more questions than it
answered, have already begun advocating for returning with an orbiter.
An
orbiter is the logical next step because it will be able to map the whole
planet and provide high resolution images of the non-encounter hemisphere,
which New Horizons was only about to image in low resolution.
Analysis
of data returned by New Horizons seems to indicate Pluto not only harbors a
subsurface ocean but likely has had that ocean since its formation four billion
years ago. This puts Pluto in the growing category of ocean worlds in our solar
system—worlds such as Ceres, Jupiter’s moons Europa and possibly Ganymede and
Callisto, Saturn’s moons Enceladus and Titan, and Neptune’s moon Triton.
It
may be that we need to recognize more subcategories of planets, specifically,
these ocean worlds, any of which could possibly harbor microbial life and
therefore completely alter our notions of what constitutes a star’s habitable
zone.
The
Pluto flyby was an exciting, thrilling accomplishment that stands in stark
contrast to the troubled times we face now. But that also makes it a statement
of hope, an Apollo moment, when people working together persevered in a long
term effort that took a decade and a half to get to launch and then nearly
another decade to reach its target. It is an inspiring achievement of people
coming together, working with limited resources, building an extremely
efficient spacecraft, and cooperating to quickly address any difficulties along
the way. Flying a piano-sized spacecraft to a small, distant planet took
precision, intellect, collaborating and problem solving—skills much needed
around the world right now to address the various crises that plague this
planet.
Beautiful
Pluto inspired and gave hope to so many people. This mission stands as a
tribute to the good people can do when they come together to work toward a
difficult, ambitious goal.
Personally,
I continue to hold the faith that scientists will succeed in returning to Pluto
with an orbiter and that this return will be in my lifetime and the lifetimes
of the many people who worked on the New Horizons mission and those who were
enthralled by it.
For
those interested, there are two new compilations of New Horizons' findings at Pluto. One
is an e-book by Astronomy magazine, titled The Strange, Icy World of Pluto,
which is available as a PDF for download at https://astronomy.com/-/media/Files/PDF/Marketing/Ebooks/Plutoebook.pdf
and an academic textbook coming out next year titled The Pluto System After New Horizons, which is available for order
at https://uapress.arizona.edu/book/the-pluto-system-after-new-horizons
.
