Ice Covered Oceans
Credit: Pacific Ring of Fire 2004 Expedition. NOAA Office of Ocean Exploration; Dr. Bob Embley, NOAA PMEL, Chief Scientist.
At least eight bodies in our solar system are thought to harbor liquid oceans.
In some cases, such as Europa and Enceladus, this ocean is perhaps habitable
and encased in an icy shell kilometers thick. To explore these worlds new
mission concepts must be developed using penetrating, submersible vehicles. The long mission duration - potentially
over a year to melt through the icy shell and a one year exploration mission -
requires a low power vehicle, limiting the types of instruments on board.
While the vehicle would ideally travel hundreds to thousands of kilometers
distant from the base station, the submersible would need to return close to
the base station to transfer data - with data subsequently relayed to an orbital platform for eventual return to Earth.
The radiation environment near the target body could preclude the use of an orbiting communication relay,
instead relying on a relay in an eccentric Jovian orbit (in the case of Europa),
increasing the time between communication windows from daily to monthly.
When the submersible is away from the base station, it would be unable to communicate with Earth.
Therefore, while making journeys further and further away from the base station,
the submersible might be operating days or weeks without contact.
During this time, the submersible would be required to autonomously detect, locate,
and study a specific feature of interest.
- Planning and Execution
- Nested Search
- Anomaly Detection
Due to the communication paradigm associated with operating an underwater submersible on an Ocean World,
the vehicle must be able to act autonomously when achieving scientific goals. One such goal is the study of
hydrothermal venting. Evidence for hydrothermal activity has been found on one Ocean World, Enceladus.
On Earth, these geological phenomena harbor unique ecosystems and are potentially critical to the origin of life.
Similar vents on Ocean Worlds could be the best chance at extra-terrestrial life in our Solar System.
We focus on performing autonomous science, specifically the localization of features of interest - such as hydrothermal venting -
with limited to no human interaction.
A field program to Karasik Seamount in the Arctic Ocean was completed in Fall 2016
to study and understand the human-in-the-loop approach to the localizing hydrothermal venting.
In 2017/2018 an autonomous nested search method for hydrothermal venting was developed
and tested in simulation using a hydrothermal plume dispersion model developed by Woods Hole Oceanographic Institution.
Simulation showing the observed plume strength during the nested search to locate the hydrothermal vent at (0,0). The simulated vehicle
performs surveys of repeatedly higher resolution until the vent source is found.
By using Earth's oceans as an analog for Ocean Worlds we can develop methods capable of
autonomously locating, detecting, and studying interesting scientific features.
While not all ocean processes on Earth are expected to recur on other Ocean Worlds distant from the
sun, we have a wealth of experience studying hydrothermal venting, thermoclines, ocean fronts,
and other structures in Earth's oceans. This knowledge can be adapted for the study of Ocean Worlds.
One compelling feature, due to the interesting ecosystems that forms around it, is hydrothermal venting.
Hydrothermal venting produces a plume of chemically altered fluid which can be detected
with instruments such as temperature, optical backscatter, and oxidation-reduction
potential sensors. This plume can then be traced back to the source.
We have developed a fully autonomous nested search strategy for the localization of
hydrothermal vents based on a manual three-phase nested search commonly used in the field.
In order to test this approach, a hydrothermal plume dispersion simulation was developed by
Woods Hole Oceanographic Institution using FVCOM, an existing ocean circulation model.
Our method is based on field proven techniques which are able to overcome the challenges of searching for hydrothermal vents.
- Jet Propulsion Laboratory, California Institute of Technology
- Steve Chien
- Andrew Branch
- Kevin P. Hand
- Woods Hole Oceanographic Institute
- Christopher R. German
- Guangyu Xu
- Michael V. Jakuba
- James C. Kinsey
- Andrew D. Bowen
- Jeffery S. Seewald
- John Hopkins University
- Louis L. Whitcomb
- Christopher McFarland
- Lehigh University
- Alfred Wegener Institute
- University of Bremen
Planetary Science and Technology from Analog Research (PSTAR), National Aeronautics and Space Administration