Scientists say when a European spacecraft orbiting a distant comet sends a small lander to settle on the comet's surface, they hope to discover a whole lists of things about the mysterious object -- including why it is "singing."

Instruments aboard the European Space Agency's Rosetta spacecraft presently circling around Comet Churyumov-Gerasimenko have detected a "song" being emitted by the comet, recorded as oscillations in the magnetic field surrounding the object.

Far below the range of human hearing -- we can discern sounds from 20 hertz to 20 kilohertz -- the comet's "song," picked up by Rosetta's magnetometer experiment, is tuned to 40 to 50 millihertz.

The cosmic tune was first detected in August as Rosetta came to within around 60 miles of the comet.

ESA scientists say they believe it may be produced as the comet emits neutral particles out into space which are then ionized, taking on an electrical charge.

However, they acknowledge that at the present that's just speculation.

"This is exciting because it is completely new to us," says Karl-Heinz Glassmeier at the Technische Universitat Braunschweig in Germany. "We did not expect this and we are still working to understand the physics of what is happening."

Researchers hope to know more, and answer a number of other comet questions as well, when Rosetta's lander, dubbed Philae, is sent to the comet's surface on Nov. 12.

Among the discoveries the Rosetta/Philae could make is a complete inventory of the chemical and mineralogical composition of the comet, and dynamic properties and shape of its nucleus.

A central question scientists hope to gather data on is when, where and how the comet formed.

Comet Churyumov-Gerasimenko is one of numerous short period comets which have orbital periods of less than 20 years, with orbits controlled by Jupiter's gravity, which is why they are also called Jupiter Family comets.

Like all comets, it has been named for its discoverers, Klim Churyumov and Svetlana Gerasimenko, who identified it from astronomical photographic plates in 1969.

Of particular interest to scientists pouring over Rosetta/Philae data will be the relationship of the materials the make up the comet with those found in interstellar space.

They also hope to determine if the comet dates from the time of the formation of our solar system, which could provide valuable clues to the processes that created the planets, including the Earth, that currently voyage around our Sun.