A tiny electronic component the size of a thumbnail holds the key to the future of an £8m search for life beneath the ice of Antarctica.
The project to drill through the ice-sheet to reach the hidden waters of Lake Ellsworth has been on hold for the past week after a boiler broke down.
The component just arrived after a journey of roughly 15,000km.
Engineers will now attempt to fit the part in the next few days in the hope of restarting drilling next week.
The drill is meant to be powered by hot water but the entire effort had to shut down when a "varistor" - a variable resistor - on the boiler's circuit board burned out. A replacement also failed.
A spare was sent from Britain via Chile to the remote camp in West Antarctica.
But tension surrounding this operation is mounting because of the uncertainty about whether the boiler will not only fire up but also whether it will continue to run for at least a week - or fail again as a result of a fundamental fault.
Another major concern is the amount of fuel being used to run a back-up boiler which is essential for keeping the drill system from freezing up.
It is likely that the system can be kept ticking over in this way for another fortnight - but any longer will use up too much fuel to power the main boiler for the drilling operation itself, assuming it starts.
In case the new component fails, another replacement is already on its way from Britain but is likely to take several more days to reach the drill site.
So the window of opportunity for a successful drilling operation is getting tight.
Should it prove impossible to carry out the drilling before winter arrives in February, one option on the horizon will be to winter-proof as much of the equipment as possible to be ready for another attempt next year.
But sources at the British Antarctic Survey say they are still determined to keep trying and that "fingers are crossed" that the new component will work.
The project's aim is to penetrate the 3km-thick ice-sheet to gather samples of water and sediment from the lake below - to answer the fascinating question of whether life is possible in conditions of total darkness and immense pressure.
Lake Ellsworth is one of nearly 400 sub-glacial lakes in Antarctica - a feature of this polar region only discovered 16 years ago.
If the drilling does start next week, the first samples could be brought to the surface a week later.