The ambitious attempt to drill through two miles of ice to reach an Antarctic lake has been called off, following problems with the boiler used to heat water for drilling.
The British Antarctic Survey team had been planning to extract samples from Lake Ellsworth, cut off from the outside world for as much as half a million years, in search of microbes or other signs of life.
Last week, the team was forced to stop work when both the main and backup boilers failed. A replacement part was successfully fitted and drilling restarted, but the team then encountered difficulties linking the main borehole with a second borehole used to recirculate drilling water back to the surface.
"On Christmas Eve we took the decision to cease our efforts to directly measure and sample Subglacial Lake Ellsworth. Although circumstances have not worked out as we would have wished, I am confident that through the huge efforts of the field team, and our colleagues in the UK, we have done as much as we possibly could have done, and I sincerely thank them all," says principal investigator Professor Martin Siegert.
"Sixteen years ago, we hypothesised that deep-water subglacial lakes are viable habitats for life, and contain important records of ice and climate history. For now, these hypotheses remain untested. Once back in the UK I will gather our consortium to seek ways in which our research efforts may continue. I remain confident that we will unlock the secrets of Lake Ellsworth in coming seasons.”
The first borehole was drilled to a depth of 300 meters and then left for 12 hours to create a cavity. The second, main borehole - located two meters away from the first - was then drilled to the same depth, and should have immediately connected with this cavity, allowing water to be recirculated back to the surface using a submersible pump.
However, for unexplained reasons, the team wasn't able to link the two boreholes, despite trying for over 20 hours. During this process, hot water seeped into the porous surface layers of ice and was lost. Digging and melting more snow wasn't enough to compensate, and fuel stocks were by now running dangerously low. The team says it had no option but to scrap the programme, at least for this season.
"This is of course, hugely frustrating for us, but we have learned a lot this year," says Siegert. "By the end the equipment was working well, and much of it has now been fully field tested. A full report on the field season will be compiled when the engineers and programme manager return to the UK.”