Collect Comet Dirt or Fly the Friendly Skies of Titan?
Should we return to
the comet visited earlier by NASA/ESA (comet 67-P/Churyumov-Gerasimenko), to
collect some material and fly it back to Earth for study, or land drones on
Saturn’s moon Titan to study that icy world in more depth? Those appear to be the deep solar system
projects (New Horizons) currently most likely to be given the green light by
NASA, according to a number of news sources.
Since I have previously blogged about the Rosetta mission to a comet,
and about some possibilities for a Titan mission, this seems like a nice
opportunity to revisit and elaborate upon those subjects.
The Rosetta mission to a comet:
Three related blogs,
based on a talk given at the University of Alberta, by a Rosetta mission
scientist, and some related papers. Naturally, I encourage you to read those blogs
for some detailed background.
Titan and Its Seas of Tranquility
A blog about Saturn’s moon Titan, particularly related to findings about likely wave action on its liquid hydrocarbon seas.
The Two Finalist Missions
NASA chose these two
missions from a dozen concepts that had been submitted. They will now receive funding (some $4
million each) for more detailed planning and analysis. The final decision is to be made in mid-2019,
with a proposed launch date of 2025. So,
if you are thinking of an running an office pool on this, it will take a while
to win the bet.
1) Dragonfly to Titan
The proposed mission
to Titan has been named The Dragonfly Mission.
The idea is to land a drone on Titan, which could fly to different
spots, and thereby return data from more than one location on the moon.
The mission would take
quite a while to make the journey to Titan, arriving in 2041. It would then release the Dragonfly lander
(or flyer/hopper), which would make a series of hops over a two year span,
surveying dunes, rivers and lakes. Naturally, it would be especially focussed
on the sorts of molecules that are the building blocks of carbon based life,
here on Earth.
We know that Titan
has these geographical features, based on findings from the earlier
Cassini-Huygens mission. In fact, we now
know that Titan has a hydrological cycle, much like the Earth’s water cycle,
with methane/ethane replacing water. That
mission mapped Titan from orbit, and dropped a lander, which returned pictures
and other data from the surface, for a short time. Unfortunately, the Huygens lander could only
transmit for a few hours, before it succumbed to the incredibly cold conditions
on Titan.
The Dragonfly probe
will last a lot longer, as it has a radioactive energy source that will keep it
going for years. Many of the other deep
space probes have also contained such a power source, so this isn’t
fundamentally new. This power source will supply cameras, spectrometers,
various other sensors, as well as a drill to analyse sub-surface samples.
Of course, flying a
drone on another world is fundamentally new, and will no doubt be rather
challenging. However, Titan has a thick
atmosphere (4 times denser than Earth’s) and low gravity (one-seventh that of
Earth), and both of those factors should enhance the prospects for flight. Since Titan’s seas were found to be tranquil,
the atmosphere ought to be reasonably tranquil as well (limited wave action on
the seas implies limited winds).
Nonetheless, it does seem to be a rather ambitious plan.
2) CAESAR to Comet 67-P
The other mission being considered involves a return to Comet
67-P, the comet visited by Rosetta in 2016.
This would involve not only a landing, but a return of a sample from the
comet. It would launch in the mid 2020s,
and eventually bring back a small sample, in the range of a few hundred grams.
This would involve capturing volatiles (off-gassing) and non-volatiles (comet
nucleus material). These could then be
analysed in great detail in labs back on Earth.
This seems like a lot of trouble to go to, to retrieve a
handful of comet dirt. But this dirt
would be special – material essentially dating from the formation of the solar
system, that would help us to understand the building blocks that eventually
formed planets, including Earth.
The big advantage of going to Comet 67-P again, is that we
have already been there once. That means
that we have detailed knowledge of its shape and have good maps of the
surface. Plus, we know that Rosetta’s
Philae lander got down safely and transmitted data for a period of time, even
if it had some bad luck that reduced its useful lifespan. Knowing that a mission has been accomplished
once, even if not 100% successfully, tends to help out mission planning
psychologically, as well as physically.
Just think of how the Dieppe raid in 1942 aided the planning for D-Day
in 1944 (or so they say).
The Likely Winner?
Assuming that one of these missions really does go ahead
(never a sure thing in space science), which one is more likely to get the
go-ahead?
From a purely technical and administrative point of view, the
comet mission seems to be more achievable, so that could account for a lot,
when the final decision is made. There
is a tendency to bet the higher odds horse, when big money is on the line (a
billion dollars or more). Plus, it would
be the first significant sample return mission since the moon landings over 50
years ago. So, that would be a point in
its favor, from both a scientific and P.R. point of view.
But from a wider scientific and shall we say romantic point
of view, I think the Titan Dragonfly plan is the winner. After all, Titan is an actual big moon with
oceans and rivers, orbiting the mysterious and beautiful planet Saturn. That’s a pretty tough image to beat. And, as always, there is some small dim hope
of life, or something like it, existing there, since it has hydrocarbons and
weather, like the Earth. “It’s life, Jim, but not as we know it.” And drones hopping around an alien moon –
what’s not to like about that? Maybe
Amazon will kick in some money for advertising rights on the drone.
My science fiction/romance writer wife is all for Titan. As she says, you could write plenty of
stories about that, whereas the comet mission seems more limiting from a
literary point of view. That may seem
scientifically irrelevant, but it is the sort of imaginative consideration that
the public cares about, and that is of critical importance.
My astrophysics
PhD/data scientist son also agrees with the Titan mission. Basically, it just seems like the step that
has greater scientific potential, given its larger scale and more ambitious
scope.
I tend to agree with
both wife and son, for the reasons given and more. Titan just sounds like a greater adventure,
and that’s what the human race needs.
A Walk on the Juan de Fuca Marine Trail
Speaking of
adventure, perhaps you would like to read about some adventure spots on our own
green and blue planet. If so, you might
consider “A Walk on the Juan de Fuca Marine Trail”, a beautiful hike on the
western shore of British Columbia, Canada.
The Juan De Fuca Marine is considered by many to be one of
Canada’s finest hiking trails. It hugs the south-western shore of Vancouver
Island, between Jordan River and Port Renfrew for a distance of about 48
kilometres. Like its (perhaps) more famous neighbouring hiking trail just to
the north, The West Coast Trail, it features both beach and forest hiking along
a rugged coastline. The hiking is a nice test of one’s fitness, the views are
spectacular, the wildlife (marine and forest) is plentiful and the people are
friendly. What more could one ask for?
What follows is a journal of a five day trip, taken in early
September of 2002. It is about 13,000 words in length (60 to 90 minutes
reading), and contains numerous photographs of the trail. There are also
sections containing a brief history of the trail, geology, flora and fauna, and
associated information.
