Cumberland Times-News

September 22, 2012

Mars mission: Send humans or robots?

Bob Doyle, Columnist
Cumberland Times-News

— One of the greatest technological accomplishments in U.S. history was the successful landing of humans on the moon and the safe return of the humans and their samples (850 pounds of moon rocks) to Earth over 40 years ago.

A similar mission to Mars will be much more difficult because of the expense and the risk of the humans involved in a two-year mission (versus an eight to 10-day mission to moon).

An easier mission to Mars would be a robotic sample collection and return mission to the Earth.

Advantages of the robotic mission include: No need for carrying a huge amount of water, food, oxygen to maintain a human crew (even if some recycling is possible), no worry about the two-year-long exposure of the humans to cosmic rays that would penetrate a Mars craft and the Mars lander, no worry about the mental health and fitness of a Mars crew.

The robotic mission price would be 20 to 40 percent of a manned mission.

Even the robotic sample and return mission would be complex. If even a robotic mission return is risky, then why should it be attempted?

The return of several hundred pounds of Martian material may allow us to answer the big question: Was there or is there life on Mars? (This would be through detection of Martian fossils or even bacteria living inside of Mars rocks).

This analysis would be done in laboratories on Earth, just as the moon rocks were analyzed. A robotic return of moon rocks was accomplished by the U.S.S.R. in the 1970’s. (This was overshadowed by the U.S.’s return of a much larger mass of moon rocks.)    

The moon rock samples led to the most likely explanation for the formation of our moon.

Early in its history, the Earth was struck by another planet, about half as big as Earth. This planet was shattered and huge amounts of the Earth’s mantle were hurled outward, which eventually led to the formation of our moon.

This possibility has been demonstrated on supercomputer simulations of a colliding planet and the Earth. Also the composition of moon rocks matches what we know of the Earth’s mantle (material hurled out of volcanoes).

This collision can also explain the Earth’s axial tilt of 23.5 degrees, which causes our seasons.

   The robots on this mission (perhaps 15 years from now) would be considerably more advanced and compact than the Mars rovers or even Curiosity.

Each robot would likely be bipedal (two feet) with two arms, two high resolution cameras for eyes (for depth perception) with a powerful on board computer so the robots could cross rugged terrain nearly as well as humans could.

The robots would be powered by high capacity batteries that could recharged when the robots would not be active (during the bitterly cold Martian nights).

The Mars craft would be assembled in low Earth orbit using robots. Rather than the extremely cold liquid hydrogen and liquid oxygen for fuel used to launch our planetary probes, the Mars craft would be powered by solid fuel rockets (reliable enough to power our submarine based nuclear missiles for decades).

The Mars craft would likely be comparable in mass to our present International Space Station (about 500,000 kilograms); its components would likely require about a half dozen launches of a heavy lift rocket (such as SpaceX’s Falcon).

The first step would be to fire the first stage rockets in the direction of the Earth’s motion about the sun to put the Mars vehicle into an orbit that would take it to Mars’ orbit on the far side of the sun.

Opportune times for launch would occur every 780 days. After a six-month flight, the Mars craft would meet Mars. Then there would be firing of rocket engines so the craft would slow down to match Mars’ orbital velocity. There would be an additional firing to put the craft into orbit about Mars.

The Mars craft would then be only about a third as long as the original craft that left Earth orbit.

The Mars lander would disengage from the Mars orbiter and with a series of controlled firings enter a spiraling path around Mars, making use the Martian atmosphere to slow its descent (aerobraking).

In the last stage of descent, several stages of parachutes would bring the Mars lander (robots aboard) to Mars’ surface.

I will continue my description of a robotic return mission to Mars in my next column. Any reader comments are welcome; email me at .

SKY SIGHTS IN WEEK AHEAD: Tonight the moon is just past first quarter phase (half full) and will grow to full late Saturday evening.

This full moon is the “Harvest Moon”, offering extra evening moonlight through early October.

My 4 p.m. talks on “Local Mammals” in Compton 224 on Sundays also feature simulations of the current evening and dawn skies. These talks last about 35 minutes and are free to the public.

Afterwards, I take any interested audience members on a tour of our Science Discovery Center on the first floor of Compton.

Bob Doyle invites any readers comments and questions. E-mail him at . He is available as a speaker on his column topics.