from Chapter 2...
Over the next three weeks I approved Craig's proposal, made sure he got the journal article, and spent many days poring over research materials, both hard and softcopy, for my master's program.
One day, as I was scanning the library's database for my bibliography, Craig stopped by to show me what he had done so far. He spread out his notes. I was impressed with the amount of reading he had already done. I could also tell something was troubling him.
"You've done quite a bit. Plan to take the rest of the summer off?" He shook his head.
"I found an article on the 'net," he said, "and I don't know what it means." He paused.
"And...?" I asked. He searched through his notes and came up with a single sheet of paper.
"This," he said, waving it gently, "refutes the contention made by David McKay and Everett Gibson, the scientists from NASA who said the meteorite came from Mars and shows definite signs of life. But it's not like the other challenges, even though there're lots of them. It seems like such a simple thing--" again he paused, "but it confuses me. I don't know what it means."
"Craig," I said, "please tell me what it is and if I don't have the answer, we can go find someone who does, okay?" He nodded and began his explanation.
"It's possible to extract gases from rocks, to find out something about the atmosphere at the time the rock was formed. We get information about earlier periods in Earth's history that way. We can also find out something about the formation of meteorites, and moon rocks and stuff like that. Now, what this says is that one of the noble gasses, argon, was found in this meteorite. That's not a big deal. You can find it on Mars, which the Viking mission did in 1976. It's also found on Earth, only in slightly different amounts. Argon makes up about 1% of Earth's atmosphere and 1.6% of the atmosphere on Mars. But if you take a ratio of two different forms of argon, you get a totally different picture. On Earth the ratio of 40 AR to 36 AR is 296. On Mars the ratio is 3000." I waited. Craig read the paper, looking for the reference.
"And in the meteorite?" I asked. He looked up.
"For the meteorite it's 1650." I sat back.
"All right. Is there any way the chemistry might have been altered by heat, cold, deterioration over time--in other words, what is the possibility that the gas has changed due to some external factor?"
Craig shook his head. "Not argon. Noble gasses don't change. They're incorruptible." He paused and I thought, good boy, a little chemistry, a little physics. Nice job so far. "It's true that contamination with water, or contact with gases might make a difference to other chemicals," he continued, "And if that's the case, then it must have come from a planet and not an asteroid. But there's something else."
I waited. My young student was completely engrossed in his work. Such dedication was rare, and I appreciated it when I found it. "According to another article, there's just no way anything from the surface of Mars could have made it to Earth." I shook my head.
"And why not...?"
"Because in order to escape the Martian surface, the rocks would have to be hit with a force great enough to send them out into space at 5 km per second. That's the escape velocity for Mars. They would have disintegrated...vaporized. Just think about it..." he was getting agitated again, "can you imagine anything coming down into Earth's atmosphere and breaking off a chunk of the Rocky Mountains and have it sail off into outer space. No way. It doesn't make any sense."
"But the atmosphere on Mars is only a tiny fraction that of Earth's and its gravity is much less. Perhaps that accounts for the difference." I didn't know much about astronomy, but I knew that much.
Craig shook his head. "I don't think so. If we could just pick up rocks from other planets, we wouldn't have gone to the moon with the Apollo Program. Wouldn't it be even easier for a moon rock, with no atmosphere at all to burn it up, even less gravity to slow it down, and an escape velocity of 2 km per second to find its way here? Wouldn't it mean that we would have all the moon rocks we wanted right here on Earth? But that's not what happens. The moon is only a quarter of a million miles from us. Mars is, like, 50 million miles away. And here's something really strange. There are more so-called 'Martian' meteorites than there are 'lunar' ones."
"Well then, your conclusion is that the meteorite is not from Mars and does not contain signs of life. So far, so good." He stood up.
"No, Mrs. Evans, that's not what I'm saying at all. The meteorite didn't come from Mars, and it didn't come from Earth. If it came from this solar system, I just can't figure out where or how. And I think it does prove there's life outside of Earth."