Erase everything you know about this rock sample.
Michael Tolland had been struggling with his own disquieting ruminations about the meteorite, but now, with Rachels probing questions, he was feeling an added unease over the issue. He looked down at the rock slice in his hand.
Pretend someone handed it to you with no explanation of where it was found or what it is. What would your analysis be?
Rachels question, Tolland knew, was loaded, and yet as an analytical exercise, it proved powerful. By discarding all the data he had been given on his arrival at the habisphere, Tolland had to admit that his analysis of the fossils was profoundly biased by a singular premise‑that the rock in which the fossils were found was a meteorite.
What if I had NOT been told about the meteorite? he asked himself. Although still unable to fathom any other explanation, Tolland allowed himself the leeway of hypothetically removing the meteorite as a pre‑supposition, and when he did, the results were somewhat unsettling. Now Tolland and Rachel, joined by a groggy Corky Marlinson, were discussing the ideas.
So, Rachel repeated, her voice intense, Mike, youre saying that if someone handed you this fossilized rock with no explanation whatsoever, you would have to conclude it was from earth.
Of course, Tolland replied. What else could I conclude? Its a far greater leap to assert youve found extraterrestrial life than it is to assert youve found a fossil of some previously undiscovered terrestrial species. Scientists discover dozens of new species every year.
Two‑foot‑long lice? Corky demanded, sounding incredulous. You would assume a bug that big is from earth?
Not now, maybe, Tolland replied, but the species doesnt necessarily have to be currently living. Its a fossil. Its 170 million years old. About the same age as our Jurassic. A lot of prehistoric fossils are oversized creatures that look shocking when we discover their fossilized remains‑enormous winged reptiles, dinosaurs, birds.
Not to be the physicist here, Mike, Corky said, but theres a serious flaw in your argument. The prehistoric creatures you just named‑dinosaurs, reptiles, birds‑they all have internal skeletons, which gives them the capability to grow to large sizes despite the earths gravity. But this fossil . . . He took the sample and held it up. These guys have exo skeletons. Theyre arthropods. Bugs. You yourself said that any bug this big could only have evolved in a low‑gravity environment. Otherwise its outer skeleton would have collapsed under its own weight.
Correct, Tolland said. This species would have collapsed under its own weight if it walked around on earth.
Corkys brow furrowed with annoyance. Well, Mike, unless some caveman was running an antigravity louse farm, I dont see how you could possibly conclude a two‑foot‑long bug is earthly in origin.
Tolland smiled inwardly to think Corky was missing such a simple point. Actually, there is another possibility. He focused closely on his friend. Corky, youre used to looking up. Look down. Theres an abundant antigravity environment right here on earth. And its been here since prehistoric times.
Corky stared. What the hell are you talking about?
Rachel also looked surprised.
Tolland pointed out the window at the moonlit sea glistening beneath the plane. The ocean.
Rachel let out a low whistle. Of course.
Water is a low‑gravity environment, Tolland explained. Everything weighs less underwater. The ocean supports enormous fragile structures that could never exist on land‑jellyfish, giant squid, ribbon eels.
Corky acquiesced, but only slightly. Fine, but the prehistoric ocean never had giant bugs.
Sure, it did. And it still does, in fact. People eat them everyday. Theyre a delicacy in most countries.
Mike, who the hell eats giant sea bugs!
Anyone who eats lobsters, crabs, and shrimp.
Crustaceans are essentially giant sea bugs, Tolland explained. Theyre a suborder of the phylum Arthropoda‑lice, crabs, spiders, insects, grasshoppers, scorpions, lobsters‑theyre all related. Theyre all species with jointed appendages and external skeletons.
Corky suddenly looked ill.
From a classification standpoint, they look a lot like bugs, Tolland explained. Horseshoe crabs resemble giant trilobites. And the claws of a lobster resemble those of a large scorpion.
Corky turned green. Okay, Ive eaten my last lobster roll.
Rachel looked fascinated. So arthropods on land stay small because the gravity selects naturally for smallness. But in the water, their bodies are buoyed up, so they can grow very large.
Exactly, Tolland said. An Alaskan king crab could be wrongly classified as a giant spider if we had limited fossil evidence.
Rachels excitement seemed to fade now to concern. Mike, again barring the issue of the meteorites apparent authenticity, tell me this: Do you think the fossils we saw at Milne could possibly have come from the ocean? Earths ocean?
Tolland felt the directness of her gaze and sensed the true weight of her question. Hypothetically, I would have to say yes. The ocean floor has sections that are 190 million years old. The same age as the fossils. And theoretically the oceans could have sustained life‑forms that looked like this.
Oh please! Corky scoffed. I cant believe what Im hearing here. Barring the issue of the meteorites authenticity? The meteorite is irrefutable. Even if earth has ocean floor the same age as that meteorite, we sure as hell dont have ocean floor that has fusion crust, anomalous nickel content, and chondrules. Youre grasping at straws.
Tolland knew Corky was right, and yet imagining the fossils as sea creatures had robbed Tolland of some of his awe over them. They seemed somehow more familiar now.
Mike, Rachel said, why didnt any of the NASA scientists consider that these fossils might be ocean creatures? Even from an ocean on another planet?
Two reasons, really. Pelagic fossil samples‑those from the ocean floor‑tend to exhibit a plethora of intermingled species. Anything living in the millions of cubic feet of life above the ocean floor will eventually die and sink to the bottom. This means the ocean floor becomes a graveyard for species from every depth, pressure, and temperature environment. But the sample at Milne was clean‑a single species. It looked more like something we might find in the desert. A brood of similar animals getting buried in a sandstorm, for example.
Rachel nodded. And the second reason you guessed land rather than sea?
Tolland shrugged. Gut instinct. Scientists have always believed space, if it were populated, would be populated by insects. And from what weve observed of space, theres a lot more dirt and rock out there than water.
Rachel fell silent.
Although . . . Tolland added. Rachel had him thinking now. Ill admit there are very deep parts of the ocean floor that oceanographers call dead zones. We dont really understand them, but they are areas in which the currents and food sources are such that almost nothing lives there. Just a few species of bottom‑dwelling scavengers. So from that standpoint, I suppose a single‑species fossil is not entirely out of the question.
Hello? Corky grumbled. Remember the fusion crust? The mid‑level nickel content? The chondrules? Why are we even talking about this?
Tolland did not reply.
This issue of the nickel content, Rachel said to Corky. Explain this to me again. The nickel content in earth rocks is either very high or very low, but in meteorites the nickel content is within a specific midrange window?
Corky bobbed his head. Precisely.
And so the nickel content in this sample falls precisely within the expected range of values.
Very close, yes.
Rachel looked surprised. Hold on. Close? Whats that supposed to mean?
Corky looked exasperated. As I explained earlier, all meteorite mineralogies are different. As scientists find new meteorites, we constantly need to update our calculations as to what we consider an acceptable nickel content for meteorites.
Rachel looked stunned as she held up the sample. So, this meteorite forced you to reevaluate what you consider acceptable nickel content in a meteorite? It fell outside the established midrange nickel window?
Only slightly, Corky fired back.
Why didnt anyone mention this?
Its a nonissue. Astrophysics is a dynamic science which is constantly being updated.
During an incredibly important analysis?
Look, Corky said with a huff, I can assure you the nickel content in that sample is a helluva lot closer to other meteorites than it is to any earth rock.
Rachel turned to Tolland. Did you know about this?
Tolland gave a reluctant nod. It hadnt seemed a major issue at the time. I was told this meteorite exhibited slightly higher nickel content than seen in other meteorites, but the NASA specialists seemed unconcerned.
For good reason! Corky interjected. The mineralogical proof here is not that the nickel content is conclusively meteoritelike, but rather that it is conclusively non‑earth‑like.
Rachel shook her head. Sorry, but in my business thats the kind of faulty logic that gets people killed. Saying a rock is non‑earth‑like doesnt prove its a meteorite. It simply proves that its not like anything weve ever seen on earth.
What the hells the difference!
Nothing, Rachel said. If youve seen every rock on earth.
Corky fell silent a moment. Okay, he finally said, ignore the nickel content if it makes you nervous. We still have a flawless fusion crust and chondrules.
Sure, Rachel said, sounding unimpressed. Two out of three aint bad.