With the recent surpriselanding of a robotic probe on Asteroid 433 Eros and missions scheduledregularly to focus on Mars, some say it's time to dust off plans to send aspacecraft to the Red Planet's two mysterious moons.

Phobos and Deimos, shadowedby the Red Planet's celebrity status, have a spotty history of exploration.

A 1988 unmanned Sovietmission to Phobos disappearedinexplicably. And a robotic venture proposed to NASA, called Aladdin, did notmake the cut in 1999 and is shelved for now. Two previous Mars missions -- theViking orbiter and Mars Global Surveyor -- went out of their way to obtainpictures of Phobos and Deimos.

But NASA's MarsOdyssey, scheduled to launch in April, will give the moons nary a wink ornod.

Researchers say that afterback-to-back failedmissions to Mars, pressure is understandably intense to keep Odysseyfocused on the primary objective. NASA cannot afford to lose anotherspacecraft, especially on some scientific side trip.

But those who study Phobosand Deimos see them as destinations, not detours.

"There is no object inthe solar system that is not worth studying, but those moons suffer from beingso close to such an interesting planet, and they've always taken a backseat," said Philip Christensen of Arizona State University, who has usedMars Global Surveyor images to make limited studies of Phobos.

Unsolved mysteries

In the 24 years since theViking orbiter returned the first closeups of the moons, revealing them to beodd shaped lumpy objects, scientists have learned almost nothing about them,Christensen laments. Despite his own research and efforts of others,"we're not progressing," he said.

Scientists still don't knowif the moons were created along with the birth of Mars, or if they are asteroids thatwere captured later. Their composition remains unknown. Mars Global Surveyorpassed within 200 miles (320 kilometers) of Phobos, and showed that the moonhad been pounded to powder by countless collisions with smaller space rocks.But how, with virtually no gravity, does Phobos hold on to this dusty debris?

Answers to these questionsand others would improve basic models of the formation and evolution of planets and of our solar system. Andothers want to know if the moons are rich in valuable metals or substances thatcould be used for spacecraft propulsion.

To get these answers,researchers say we need to chip away at the rocks.

"Asteroids and smallmoons are tough to study remotely," Christensen told SPACE.com,"because they're so churned up and so bombarded by everything from thesolar wind to micrometeorites to large objects that slam into them. And it'snot clear what the outer meter or so of the surface is telling us about theinterior."

Next Page: Make Deimos aSpace Port