Lunar South Pole Landing Sites Studied

space.com ^ | 5 Jun 03 | Leonard David

[RightWhale]

Lunar South Pole Landing Sites Studied

By Leonard David Senior Space Writer

posted: 07:00 am ET 04 June 2003

NASA has taken the first tentative steps in rekindling agency interest in the Moon. As part of its New Frontiers spacecraft plans, NASA has requested proposals for a South Pole-Aitken (SPA) Basin Sample Return project.
Past robotic spacecraft orbiting the Moon have spotted what appear to be super-cold stashes of water ice. These reservoirs are seemingly tucked away in craters, hidden from the Sun's thawing rays. The Moon's South Pole is thought by many scientists to be loaded with tons of water ice. If available, this treasure trove resource could help support return-to-the-Moon expeditions To do so, processing machines would convert the water ice into oxygen, drinkable water, and rocket fuel. By churning out these products, living off the Moon might more easily become a way of life for future explorers.

SPA is the largest, oldest preserved lunar basin. Debris ejected from the feature when it was created, as well as the basin's rim, contains material from the lower crust and possibly the upper mantle of the Moon. Snagging compositionally unique samples from there should yield insight into the very early history of the Earth-Moon system.
If given a go-ahead, a sample return craft may be hurled moonward before decade's end. It is a journey that only takes three days, unlike the six month, one-way missions to Mars that NASA is currently preparing for launch. That mission could well set the stage for a more aggressive reconnection with Earth's Moon, first using advanced robots, followed by humans that go the lunar distance.

Shadowy past

Taking a hard look at prospective landing sites at the lunar South Pole is Philip Stooke, a space scientist at the Departments of Geography and Physics and Astronomy at the University of Western Ontario in London, Ontario, Canada. "The lunar South Pole is interesting for its proximity to the South Pole-Aitken basin and the potential for volatile materials -- including water -- in perpetually shaded areas," Stooke said. Finding that water would help bolster the prospects for future human settlement of the Moon, he said. Within that moonscape, there is also an area informally known as the 'peak of eternal light' -- a ridge between the rims of several craters. It receives sunlight nearly all the time, though no single spot is permanently illuminated..

Landing robotic machinery in an area of nearly continual sunlight helps deal with issues of thermal control and power generation. Therefore, Stooke points out, the peak of eternal light is considered a prime landing target region.

Rover routing

Stooke asked himself: Given that this area on the Moon is a potential target, how do we get to select spots and maximize rover operations?

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In his assessment, Stooke took into account four things: .
Good lighting - that is, long periods of sunlight; .
Good view from Earth, a factor that cut out half of the well-lit area; .
Feasible rover routes into craters; and .
Small fresh craters (giving the freshest regolith for samples of South Pole-Aitken basin ejecta (recycled through multiple impacts since then, but still SPA material).

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"Add all these factors and you can identify several good landing points, which is what I have tried to do. I'd like to see a mission like this, perhaps as a follow on to the SPA sample return mission," Stooke said.

Landing zones

In utilizing imagery taken in 1994 by the U.S. Pentagon's Clementine spacecraft, Stooke has tagged seven landing zones, areas from which a rover might have access to nearby, permanently shaded terrain. Several of the spots -- 2, 5 and 7 -- are essentially those once considered by the European Space Agency under the rubric of the now defunct EuroMoon 2000 project..
To best sample SPA rim material, Stooke said, sites are chosen on the ejecta blankets of Shackleton and de Gerlache craters (which cover the whole 'peak'), but adjacent to small craters which will have excavated, fresher material from under the local weathered lunar regolith. Sites 1 and 2 are on the rim of Shackleton. Both allow rover access to the interior of Shackleton, but its young age may mean its walls are too steep for safe driving and its volatile content may be low. Sites 3, 5 and 6 offer short and easy drives into a nearby crater, but its small size may limit its volatile reservoir potential. Site 4 offers lengthy -- over 12-miles (20 kilometers) -- drives into a crater that appears to be older than Shackleton, so it may have accumulated more volatiles and have shallower interior slopes. An Earth-Moon radio ink could only be via the lander remaining at site 4 (or relays deployed along the way) as the 'peak' will hide Earth for much of the route. Site 7 offers several pathways into de Gerlache crater, including a short direct trek if the walls are shallow enough, as well as longer diagonal routes. In Stooke's view, the set of wished-for landing sites offer access to SPA material and volatiles. Sites 4 and 7 are probably the best for access to volatiles because of the size of the dark areas and the shallower slopes on the rover route. But there is a caveat to this lunar research. Knowledge of lunar topography is extremely limited in this area because of the effects of shadowing in both Clementine images and Earth-based radar, especially inside craters. So a detailed analysis of route safety and communications is not yet possible, Stooke said. .
People have long been interested in the lunar poles, even before the former Soviet Union boosted Sputnik 1 into Earth orbit, Stooke said. As early as 1955, the Soviets were scripting a plan a remote controlled lunar rover at one of the poles, he told SPACE.com . Furthermore, in 1961, the Nobel Prize winning American cosmochemist, Harold Urey, identified possible ice at the poles as a target for lunar exploration. So the idea is not new, and interest in scouting out polar ice has grown with NASA's Lunar Prospector data that was gathered in 1998-1999.

Communications blackout

One thought stemming from Stooke's research is how best to handle Earth-Moon communications. "It's tricky at the poles because the Moon's axis is tilted about 5 degrees off the Earth-Moon line. So if you're at the pole, Earth is sometimes five degrees above the horizon, which is good. But sometimes it's five degrees below the horizon. Then you have a communications blackout. Periods of no communication would last a bit less than two weeks," Stooke said. .
One solution is a relay station at about 85 degrees latitude on the Moon's near side. But Stooke offers another alternative. "Not perfect but quite good and probably easier in the near term is communication with satellites in geostationary orbit," the researcher points out. "The geostationary orbit is tilted such that, not all the time but frequently, when Earth is below the polar horizon some geostationary satellites are not. Given suitable radio equipment on a few geostationary satellites, they could cover most of the blackout periods at the Moon's pole. I would fly lunar communication equipment piggyback on satellites normally dedicated to other purposes," Stooke suggests. "My work is intended to help plan a necessary intermediate step, getting robotic rovers into the area to examine the ice. This is not an active mission, of course, but it could be one soon," Stooke concluded

[RightWhale]

Things could hardly move slower.

[KellyAdmirer]

Enough robots (that will probably break down like all the Mars probes) already. Unbelievable. What is wrong with NASA? Plan to send a manned mission back to the moon already! Junk the obsolete shuttle if necessary, nobody gives a hoot about dangerous and totally unproductive low earth orbits anymore. We have to wait years longer just to examine more moon rocks? NASA needs somebody with some vision, which has been sorely lacking there.

[demosthenes the elder]

this is taking bloody forever.

[demosthenes the elder]

someone explain to me: why are we building a hugely expensive space station which has no capacity to serve as an assembly dock for terra-lunar shuttles?

[WhiteGuy]

What a huge waste of OUR money.....................

What do we hope to see as a return on OUR investment?

Tang still sucks and I haven't seen "Space Food Sticks" at Krogers for years.

Zero out this foolishness.

[RightWhale]

What do we hope to see as a return on OUR investment?

That's right, it is a centralized group project. Individual taxpayers do not get to choose how their money is spent, instead, the Central Committee [Congress] decides. It's kind of amazing anything gets done at all considering most of their plans are knee-jerk responses to impending crises.

There is a better way. There must be.

[mvpel]

If there were dried concrete on the Moon, settlers would mine it for its water. The Moon is that dry. This is why the presence of easily available water on the Moon would be an incalculable boon for lunar exploration and settlement.

[RightWhale]

why are we building a hugely expensive space station

That's what you get when you put the Vice President, Al 'Mister Wizard' Gore in charge of NASA.

[RightWhale]

Short term: haul water.

If there is some water in the polar region, that will help the initial development of a settlement. But you might find the hauling of water to be about as effective as setting up water extraction plants.

Long term: smash carbonaceous chondrite asteroids and comets into the moon and mine those for volatiles.

[mvpel]

Or better yet, go to Mars - compared to the Moon, there's vast amounts of water there, and the delta-V is not that much higher.

[demosthenes the elder]

it is a matter of practicality.
A practical program of expansion would start with establishing routine orbit-to-orbit transit from earth to the moon and back, ferrying equipment and supplies to construction sites. Once that is stable and reliable, the risk inherent in establishing ship production facilities on the moon becomes one that can be faced. Once those manufactories are established, large interplanetary-capable ships could then be built and launched from the moon, with no need to worry about environmental effects and at a much lower energy requirement for surface-to-orbit transit than is required for terran launch. THEN it would be appropriate to extend the process to Mars and the asteroid belt.

[Junior]

The Chinese are going to put a manned base on the Moon, and all we can do is send robots. Abolish NASA now!

[mvpel]

The bulk of the Delta-V is in getting from the Earth's surface to Low-Earth Orbit. From there to the Lunar surface, you need 6.2 km/s of velocity change, versus 4.8 km/s from LEO to the surface of Mars.

With the lift capacity that we scrapped thirty years ago and which is now rotting away at Johnson Space Center's tourist attraction, along with some clever approaches that Werner von Braun never thought of in his musings of Battlestar Galactica-style Mars missions, we could mount a manned mission directly to Mars.

[demosthenes the elder]

I favor nuclear hydrogen rockets, myself.
I have heard that a Florida University has started building a refined testbed engine based on the old Kiwi family, taking advantage of modertn materials ans production/design sciences.
Well and good.
The problem remains the expense of getting mass off of earth's surface. 9.8m/s*s is a bitch no matter how you slice it. It is also environmentally unsound.
A one-shot to Mars is no big deal, but it is not a practical step in an ongoing process of expansion.
Such a process calls for routine flights of MANY ships to and from the objective. Fast ones. Big ones, too. To meet that requirement, building ships on the moon and launching them from the moon makes MUCH better sense.

[mvpel]

I guess the priorities shift depending on whether your goal is to explore and settle Mars, or to use the notion of footprints on Mars to drive a massive spacebound infrastructure project.

[demosthenes the elder]

I have in mind more a "rape the solar system of its resources for economic and strategic profit" kinda thing.

[mvpel]

That's a worthy goal, certainly.

But considering that concrete has more water than the average lunar rock, while on Mars there may well be vast aquifers of liquid water within drilling distance, and you can make air and rocket fuel out of a bit of hydrogen plus the Martian atmosphere using 19th Century technology instead of having to melt rocks, and you can make pure iron on Mars through reaction of the ubiquitous iron oxide with hydrogen, and plastics through reaction of the carbon monoxide left over from making oxygen with the atmosphere, the fact that you can grow crops under Martian sunshine, and so on, Mars has all the ingredients needed for a self-sustaining branch of civilization.

[demosthenes the elder]

true, all. however, getting from here to there without the intermediate step of building a fleet of true haulers is impractical if not impossible. I am not arguing that the moon will ever be a viable colony site. Neither were various dimestamp islands during the european conquest of earth. Like those islands, however, the moon can and should serve as a useful waystation, and should serve as a primary build site for the ships we will need.
side-note: for strategic reasons, the US really ought to establish a permanent military presence on the moon, with a heavy-capacity mass-driver. We certainly can NOT let the damned ChiComs do so.

[FierceDraka]

I think you and I have been reading the same books, my friend.

[Fiddlstix]

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