Little Dome C - Beyond EPICA Oldest Ice Drilling Site (75.29917 °S, 122.44516 °E) – Season 2022/23

One small screw – lost and found

After the change to the 4-meter core barrel drill yesterday evening, and with three good runs, we continued with the longer core system this morning. After two runs of over three meters, we had some bad luck: one of the three spring-loaded pins that lock the hollow shaft onto the drive shaft of the motor popped out when re-mounting the hollow shaft. Further inspection revealed that the screw that held the locking pin in the mount had been lost. The suspicion was that the screw had been lost during the previous run, and fallen into the borehole, or with some luck had managed to be caught in the chip chamber. We spent a messy thirty minutes trawling through the chippings/fluid slurry from the last run (which comes out of the drill at a temperature of abput -50°C) trying to locate the pin, but couldn’t find it.

Hoping that we had simply missed the screw somewhere, we continued to drill, but the next few runs ended short, and with a high current, suggesting that the lost screw was down the hole, and interfering with the cutting of ice by the drill head. Surprisingly, we saw no damage to the cutters which is normal in this situation, and meant that we were not really certain that the screw was the cause of the short runs and high closing current.

However, during the last shift of the day, the run ended after only 14 cm of penetration with a sudden surge to a high current, and the drill motor stalling. Bringing the drill back to the surface revealed the lost screw jammed between the inner and outer barrel. No damage done, we will continue drilling.

End of day statistics:

Individual runs of the drill were recorded as: 3.36, 3.27, 1.64, 2.24, 2.22 0.14, 2.17 m

• Drillers’ depth: 370.03 m; daily total 16.05 m
• Loggers’ depth: 374.91 m; daily total 16.09 m
• Processors’ depth: not known today