Angry Moon

Chapter 33b

The table computer was six feet across. They all gathered around it while Samantha pulled up a pre-Scatter Cloud map of the moon.

"Okay," she said. "The thing is, the moon is way more fractured than most people think. It's been bombarded by meteors and small asteroids for four and a half billion years, and every impact breaks up the crust a little bit more. On earth, the crust heals itself. Water flows through cracks and fissures depositing dissolved chemicals, gluing the pieces together again. This doesn't happen on the moon. Any fissure that forms in a piece of rock stays there forever."

"Isn't there vacuum welding on the moon?" asked James.

"Vacuum welding isn't what most people think. Two surfaces in a vacuum can stick together, but they don't join. They can still slip and slide. The only things on the moon that can stick bits of rock together are ice and magma, and with the temperature up there rising all the time we can't count on ice."

"But there's certainly enough magma up there at the moment," said Frank.

"Indeed, but we need magma that's flowed into ancient cracks and solidified again. We need places that have been flooded by magma and that have suffered very little cratering since."

"The seas," said Ben. "The maria."

"Indeed. The sites of massive impacts billions of years ago. Places where an asteroid punched clean through the moon's crust, allowing molten rock to well up and fill the crater." She indicated the dark areas on the lunar map. "Also, it has to be somewhere in this area, the area directly opposite the magma ocean, because this will be the centre of the prograde area during apogee."

"The...?" said Alice.

"Sorry. The part of the moon's surface facing forward as it moves through space. And apogee is when the moon's furthest from Earth. Sorry, I'm so used to talking to people familiar with astronomical terms..."

"Yes, of course," said Alice, smiling. "I remember now. I just needed my memory jogging."

Samantha touched the table and rotated the image to bring the moon's eastern hemisphere to the front. "The largest sea in that area is this one. Mare Fecunditatis. The Sea of Fertility. Fortunately, it is very lightly cratered. It's a vast basin of solidified magma eight hundred and forty kilometres across. It has a region here, on its north west. A place called Sinus Successus. The Bay of Success. Almost exactly in the area you want."

Ben nodded. "Yes, I was already thinking that. The Bay of Success is a hundred and thirty kilometres across, though. We need to narrow it down a little."

"Well, I assume the closer to the prograde point, the better. Also, even the maria are covered by a layer of loose rock, regolith, that can be several metres deep. I assume you need an area of bare bedrock. Something you can firmly attach a cable to."

"That would be correct," said Kate.

"So you need a small meteor crater. Something small enough to have cleared the regolith from the area but not big enough to have seriously fractured the bedrock itself. A crater around a hundred metres across, say." She zoomed in closer. From far out, the Bay of Success looked smooth and featureless, but as she zoomed in features that had been invisible came into view. Craters, wide but low ridges and valleys. Fissures where the ancient magma bedrock had shrunk as it cooled. The occasional boulder thrown up by a large impact elsewhere on the moon.

"Well, as you can see, there are quite a few craters of the right size," said Samantha. "A couple of dozen, actually. Will any of them do or are there other criteria they have to satisfy?"

"There has to be an area within easy walking distance where the shuttle can land," said Ben. "It doesn't matter if the landing gear's wrecked. They'll be using the Chinese shuttle to land back on Earth. They just need a place a couple of miles long that they can belly flop on. Somewhere reasonably smooth and flat and without any boulders large enough to do any really serious damage to the craft. It needs the crew to survive and for the engines to still work. Other than that, it doesn't matter how smashed up it gets." He leaned forward to see the image on the table better. "I thought at first that the whole area looked promising, but now..."