astronomical unit from the Sun, so the same
distance that we are from the Sun. It could be
around the other side of the Sun, although we
would prefer it not to be because we want to be able
to see it with Earth telescopes at the same time.”
Once a target is spotted, Comet Interceptor will
leave its position at L2 and make its way towards
it, likely taking several months or years to reach
the target. Once it reaches its target, however, it will
not be able to enter orbit – like the ESA’s Rosetta
mission did around Comet 67P in 2014 – owing to
the great velocities involved. Instead it will merely
f ly past, using a suite of instruments to study the
comet as it does so – including mapping its surface,
snapping images and measuring its composition.
The f lyby will last just a matter of minutes, and
the main spacecraft will likely f ly past at a distance
of about 1,000 kilometres (600 miles). This is
because as the comet approaches the Sun for the
first time, it is likely to become very active as its icy
surface melts, throwing lots of debris into space into
a coma that surrounds the comet’s solid nucleus
that could damage the spacecraft. However, to get a
closer look Comet Interceptor will also carry with
it two smaller spacecraft, which will be sent much
closer to the comet.These will be equipped with shields at their
front to def lect debris, and will be sent on much
riskier excursions near the comet. They are more
expendable than the main mothership, so the
team will be more willing to take risks with them
and send them closer to get better views and data.
These smaller spacecraft have only been named
B1 and B2 so far – and one of them will be built by
the Japanese space agency, JAXA – while the larger
spacecraft has only been named A for now.
Studying a long-period comet like this close-up
for the first time has lots of interesting possibilities.
While we have sent many spacecraft to comets
before, including the aforementioned Rosetta
mission, these have all been short-period comets.
As these regularly orbit the Sun, their surfaces have
been dramatically altered over time. Looking at a
long-period comet, however, could give us a glimpse
back into the dawn of the Solar System itself, and
perhaps provide hints as to the origin of water and
even life on Earth.
“Long-period comets are the ones that have orbits
over 200 years,” said research assistant Dr Ashley
King, an expert in asteroids and comets from the
Natural History Museum in London. “They tend to
have really elliptical orbits, and these things come“Going to a dynamically new comet from
the Oort Cloud is something we’ve never
done before” Dr Colin Snodgrass
Studying aalien woorlds
Launching with Comet
Interceptor, ARIEL will seek out
andstudyexoplanets©NASA© NASA/JPL-Caltech© Illustration by Adrian Mann
ARIEL'stelescope
TheAtmosphericRemote-sensing
InfraredExoplanetLarge-survey
missionwillusea metre-class
telescopethatwilloperateatvisible
andinfraredwavelengths.ARIEL'saims
Usinga mixtureofinstruments
anda telescope,thespacecraft's
keymissionistodiscoverwhat
conditionsarerequiredforplanet
formationandtheemergenceoflife.Essential
exoplanet
ingredients
ARIELwillseek
outwatervapour,
methaneand
carbondioxide,
focusingonwarm
andhotworlds.Exoplanet
composition
ARIEL'sveryfirsttaskis
dedicatedtomeasuring
anexoplanet'schemical
make-up,particularlyof
transitingstars.Comet Interceptor