No worthless, awkward, greenie, P.C. solar panels to power this craft

'Boat' could explore Saturn moon
By Jonathan Amos
Science correspondent, BBC News, San Francisco

A daring proposal to try to put a "boat" down on a sea of Saturn's
moon Titan is about to be submitted to Nasa.

The scientific team behind the idea is targeting Ligeia Mare, a vast
body of liquid methane sited in the high north of Saturn's largest
moon.

The concept will be suggested to the US space agency for one of its
future mission opportunities that will test a novel power system.

It would be the first exploration of a planetary sea beyond Earth.

"It is something that would really capture the imagination," said Dr
Ellen Stofan, from Proxemy Research, who leads the study team.

"The story of human exploration on Earth has been one of navigation
and seafaring, and the idea that we could explore for the first time
an extraterrestrial sea I think would be mind-blowing for most
people," she told BBC News.

Dr Stofan, who is also an honorary professor at University College
London, has been describing her group's idea here at the American
Geophysical Union's (AGU) Fall Meeting, the world's largest annual
gathering of Earth scientists.

Low cost

The Cassini mission currently in orbit around Saturn has confirmed the
haze-shrouded moon Titan to be an extraordinary place.

Great lakes exist on its surface, fed by rivers that wash down valleys
whenever it rains.
# TITAN MARE EXPLORER (TiME) A Nasa Discovery Class proposal, powered
by ASRG technology
# Simple mission concept would hope to be low cost - $425m
# Launch 2016; Earth and Jupiter flybys; splash-down 2023
# Science payload: Mass spectrometer, sonar, meteorology and imaging
instruments

In many respects, it resembles Earth and the way it cycles water
between the surface and the atmosphere, except in the frigid
temperatures of Titan it is not water but liquid hydrocarbons that are
in constant circulation.

Scientists got a few brief hours worth of data back from Titan's land
surface in 2005 when the Huygens probe touched down in an equatorial
region of the moon.

Now a number of those same researchers are desperate to go back for a
longer-lived stay, but to investigate this time the huge pools that
contain methane, ethane, propane and probably many other types of
hydrocarbon (carbon-rich) compounds.

The Titan Mare Explorer (TiME) has already been under study for about
two years. It is envisaged as a relatively low-cost endeavour - in the
low $400m range.

It could launch in January 2016, and make some flybys of Earth and
Jupiter to pick up the gravitational energy it would need to head
straight at the Saturnian moon for a splash down in June 2023.

The scientists have a couple of seas in mind for their off-world
maritime research vessel. Ligeia Mare and Kraken Mare are both about
500km across.

Earth relevance

The primary objective of the mission would be to determine the precise
chemistry of one of these lakes; but also to do meteorology, to help
scientists better understand how the "methane-ologic cycle" on Titan
actually works.

"The key instrument is a mass spectrometer because you want to know
what the lake is made of, but we also want to do things like depth-
sounding," said Dr Stofan.

"We suspect from Cassini radar data that the lakes are many metres
deep, but we'd love to know the overall shape of the lake basins.

"Other instruments would test different properties of the lake which
would give you a handle on how the density of the liquid varied as the
craft drifted along."

According to team-member Dr Ralph Lorenz, what we learn from Titan's
lakes could be relevant here on Earth.

It would give scientists the opportunity to study shared climate
processes at work under very different conditions.

"If we have models that will work on Earth and on Titan then we can be
much more confident that those models understand the fundamentals of
what's going on," explained the researcher from the Johns Hopkins
University Applied Physics Laboratory.

"The photogenic appeal and the mystique of exploring a sea on another
world speak for themselves, but there is a genuine practical
application to do with the science that will help us address problems
here on Earth."

Mission sequence

Pictures will be essential, though. The Huygens lander sent back a
vista of orange pebbles - one of the most iconic images in Solar
System exploration history. A view from the surface of a methane lake,
looking towards the shore would be just as amazing.

Nasa and Esa (European Space agency) are currently considering a joint
multi-billion-dollar mission to the outer planets, but they have the
Jupiter system and not Saturn as their next priority.

If TiME is to make it off the launch pad it will have to grasp one of
the smaller mission opportunities that Nasa periodically offers, such
as the one it runs under its Discovery Class programme. Bids for this
opportunity will be invited in the coming months.

The agency will be considering mission concepts that can carry an
Advanced Stirling Radioisotope Generator (ASRG). This is a plutonium-
driven device that produces power far more efficiently than the
traditional Radioisotope Thermoelectric Generators (RTGs) used
hitherto on space missions, such as on Cassini.

ASRGs would give TiME sufficient energy to support a very capable
instrument suite and a direct-to-Earth communications system to get
its data home. The generators - TiME would carry two - could
conceivably sustain several years of service on the lake surface.

Whatever the outcome of the Discovery competition - and there will be
many bids from other mission hopefuls - Dr Lorenz believes the
scientific case for going to Titan is compelling, and he envisages the
orangey moon becoming a popular destination in the decades ahead.

"I think the range of science questions that there are there, and the
methodologies and types of vehicle that we use to address that
science, is going to follow very much the Mars model - we'll have one
mission building on the success of another and exploring different
questions," he told BBC News.

"Hopefully, TiME will just be the first of many exciting missions to
Titan."