The rubber ducks have Dr Behar's email address on them
Ninety bathtub toys were hurled into a drainage hole on the Greenland ice in September - an experiment to see how melt waters find their way to the base of the ice sheet.
It was hoped the ducks would flow along subglacial channels and eventually pop out into the sea. They may still, but nothing has been seen of them so far.
"We haven't heard anything from them yet," said Nasa's Alberto Behar. "If somebody does find one, it will be a great breakthrough for us."
Dr Behar is a robotics expert with the agency at its Jet Propulsion Laboratory in Pasadena. He has been studying the tubular crevasses that appear on the surface of the Greenland ice known as moulins.
These "plug holes" can drain vast lakes of melt water that settle on the top of the ice during summer months. Scientists would like to know how and to what extent this water can help lubricate the base of the ice sheet, moving it faster towards the ocean.