Situation Report #27, 15. January 2020

Little Dome C - Beyond EPICA Drilling Site (75.29917 degS, 122.44516 degE)

Personnel: Saverio Panichi (ENEA), Michele Scalet (ENEA), Jakob Schwander (unibe), Thomas Stocker (unibe), Remo Walther (unibe), Massimo Frezzotti (U Roma 3)

Weather: covered sky, moderate winds

Massimo and Michele left for Dome C to pick up the computer for the PB300. They will be back this evening.

At Radix we decided to investigate the 243 m long bore hole that has been drilled so far. The logger, designed by Jakob and developed in collaboration with a startup company from the University of Bern, is battery powered. It is lowered on the fibre optic cable which sends the logging information to the surface in real time. We register temperature and three components of acceleration, and photomultipliers receive the scattered blue light from a light source located higher up at the logger. The latter should enable us to estimate the dust content of the ice and hence reveal the presence of an ice age with strong light signal, or an interglacial with weak signal. Furthermore, sensors for the magnetic field are installed, but it turned out that they cannot be used due to a strong temperature bias. In the accessible depth range we are only interested in temperature and acceleration, the latter providing information about the inclination of the bore hole.

When we completed the casing we measured a deviation from the vertical of about 5° at the bottom of the casing. This was not ideal but judged acceptable for initiation of drilling. To our surprise and regret, today we obtain readings of the acceleration sensors that indicate an inclination of the bore hole of about 40° at a depth of 225 m! This is very bad news indeed, as it strongly suggests that further drilling in this hole does not make sense. The continuous measurements show that the deviation from the vertical is monotonously increasing to this unacceptable value. Based on our data we can exclude a vertically downward spiral with continuously increasing slope, but we think that the borehole lies in an approximately vertical plane. Unfortunately, we have no information as to the azimuthal orientation of this plane. 

We are now considering the various reasons that could have caused the deviation of the Radix drill from the vertical. As noted in several previous SitReps, we found weak or missing self-pull of the current drill design that should have been enabled by the pilot drill head mounted at the centre. The additional push that we have applied from the surface has likely contributed to the tendency of the drill to deviate from the vertical path. This is compounded by the fact that the 2 m long, slender Radix drill is not absolutely stiff but bends slightly under its own weight. As of the writing of this final SitRep from BELDC, we are considering various options where we go from here. 

Radix drilling depth: 245.7 m.

LDC, 15.1.2020