Because they don't want to scan all of Antarctica by hand?
The meteorites on the surface can be seen from far away. They need to use some sort of detector than can spot the hidden meteorites from far away - perhaps radar or ultra-high sensitivity magnetic field detectors.
How about a magnetometer? Pull it on a sled behind dogs or an ATV. They won’t have to do the whole continent by hand. They are in an area where the meteorites are concentrated by ice movement so that limits the area to cover, too.
ground penetrating radar in a towed array.