Conclusion of 2009 Expedition

February 9, 2010

Thank you for following my blog and for your comments and questions. I have been aiming to write a wrap-up/summary post since long but other tasks have kept me from it. Here I  summarize our achievements for 2008 and 2009.

ENDURANCE (Environmentally Non-Disturbing Under-ice Robotic Antarctic Explorer)  is a hovering autonomous underwater vehicle.  It was developed under NASA’s ASTEP (Astrobiology Science and Technology for Exploring Planets)  program by Stone Aerospace as a platform for developing and testing technologies for discovery of life forms on watery moons such as Europa.

The robot ENDURANCE.

Europa is one of Jupiter’s satellites and there is strong evidence that it has a rocky core separated by saline liquid water from an ice/water crust about 80-170 km thick.

A visualization of Europa showing the ice crust (white), metallic core (brown) and liquid water (blue). Photograph available under public domain from http://photojournal.jpl.nasa.gov/catalog/PIA01130.

Some of the closest analogues to Europa’s  ice-covered saline ocean on earth are the lakes in the McMurdo Dry Valleys in Antarctica. The McMurdo Dry Valleys are the largest ice-free region in Antarctica with a total area of about 4800 square kilometers.  These dry valleys are a polar desert environment with mean annual temperatures of the valley floor between -30 Celsius to -14.8 Celsius and precipitation of less than 10 cm per year.  There are about 20 lakes in the Dry Valleys almost all of which maintain a perennial ice-cover (2.8-6.0 m) over liquid water. The low temperatures, the perennial ice-cover, and the presence of microbial life make the lakes in the Dry Valleys an ideal environment for testing the concepts and technology for discovering life-forms on Europa.

Map of the McMurdo Dry Valleys. Map available under public domain from United States Geological Survey. http://wy.water.usgs.gov/projects/antarctica/htms/map2.htm

One such lake, Lake Bonney, was chosen for field testing of ENDURANCE.

Photograph of Lake Bonney. The large body of snow at the back is Taylor glacier.

Aerial view of Lake Bonney. Lake Bonney is located in Taylor valley and consists of two lobes - the west lobe and the east lobe connected by a channel. The dimensions of the west lobe are approximately 3 km x 1.5 km, with a maximum depth of about 40 m. Under the ice cover lies a freshwater lens which extends down to a sharp halocline (a sharp salinity gradient) at a depth of about 12 m. Below the halocline is a salty body of water which reaches a salinity of about four times seawater at its greatest depths. Taylor Glacier, an outlet glacier of the east Antarctic ice sheet, flows into the west end of the west lobe.

ENDURANCE performed scientific missions over 10 weeks ( 4 weeks in 2008 and 6 weeks in 2009) in Lake Bonney. With ENDURANCE we  developed and demonstrated the technology for exploring under-ice lakes for life-forms.

1.  Our vehicle was able to reach within five meters of a specified target and came back to within five meters of the melt-hole after traveling a distance of as much as 3.2 km.

2.  We developed a visual homing algorithm that allows the robot to distinguish a blinking light source and  use it to rise through a melt-hole with tight clearances.

3.  We developed a profiling system that can collect bio-geochemical data and take lake-bottom images along the entire depth of the lake and at any specified location in the lake.

4.  We obtained bathymetric maps of the underwater part of Taylor glacier and the lake bottom using sonars. This is the first time that such a detailed map has been constructed.

5. We obtained close-up visual imaging of the underwater part of  Taylor glacier at selected locations.

If you are interested in more details, please visit my publications page.


Dec 2 – Profiling the narrows again

December 10, 2009

John thought that it would be a good idea to profile the narrows again so that he could see the variation in properties with respect to time. We profiled the narrows again yesterday. This time, the mission seemed very easy and went very smoothly. Below is a plot of the narrows (from Bill) using the data from the previous run.

Plot of the narrows from sonar data. The narrows refers to the narrow channel that connects the east lobe to the west lobe. In this view, we are looking from the east side. The points are color coded, so the green points are at a lesser depth than the blue ones. About 100 years back (1903), Scott's team travelled through this region and took various measurements. This channel was much narrower back then. (Sorry no numbers, Peter mentioned their values, but I don't remember them anymore).


Nov 26-27 – Fully autonomous missions

December 4, 2009

We  finished our major science missions – profiling and glacier exploration. Our next goal is to obtain reasonably good bathymetry of the lake bottom. We obtained partial coverage last year, and we will attempt to fill in the gaps this year. We ran fully autonomous missions with zero manual intervention during the missions.  These missions are easy for all of us and it was nice to relax and just watch the data flow. More on this later.

Bathymetry coverage of West Lake Bonney obtained during 2008 missions.