Systematic Destiny (Part 3)

This story is part of our series inspired by our conversation with Dr. Joel Green of the Space Telescope Science Institute and set in the sci-fi universe of Civilization: Beyond Earth. For part 2 of the story, click here, and return next week as we continue!

“Father,” I intoned darkly, stirring my tea once more, “I see a dot on a page.”

The simple monochromatic plot revealed a tiny orb, barely visible above the fuzz of the background.

He smiled, “It is so much more than that. This just one frequency of light. The spectrum reveals so much more.” He picked up a pebble from the dirt inside the tent. “Forsterite crystals – peridot – resonate in the infrared. Our Earth is built on this. The disk that formed this ‘dot’ was rich in it. Shocks stirred the icy dust, drifting in rapidly rotating gas, agglomerating into bigger and bigger rocks, until finally the planet was made whole.”

“But how do we know it’s not a big ball of gas, like Jupiter?”

“The shadow.”

“I don’t follow.”

My father paused. “The planet passed in front its host star. The shadow of the planet dimmed the star by shading a tiny portion of it, here,” he indicated a dip of datapoints on the unremarkable chart, “here, and here. Three orbits. Not a starspot masquerading as a planet.”

“But how does that tell us the planet is solid?”

“The time. The time it took for the shadow to fully diminish the starlight. Like an eclipse. The shadow moves slowly across the surface, and from the time to reach a full eclipse…”

“…we can deduce the size of the eclipsing object, the planet.” I finished. “And because we know how massive the planet is, by its orbit and its mass ratio with the host star, we can figure out the density. Rock is denser than gas. I understand now.”

My father watched my excitement build. “What else can we learn?”

I pondered. “The atmosphere of the planet?”

“How?”

“When the shadow of the planet passes in front of the star, its atmosphere blocks part of the starlight – so we can figure out the atmosphere by contrasting it with the unblocked starlight.”

“Which would tell us…”

“The gases in the atmosphere are changed by denizens of the planet. Could we detect life that way? Is that planet inhabited?”

“With enough time and a big enough telescope, we could.” His eyes fell. “But we cannot afford that now.”

I felt cold, and pulled the blanket over my chair, brushing off the collected dust. “But if this planet is not inhabitable, we will all perish. There can be no other places to go, only one habitable zone.”

“Not necessarily. What is the key ingredient for life?”

“Water,” I answered unhesitatingly.

“Why?”

“I’m not sure.”

“Water flows.” He stirred his cup. “Water facilitates chemistry; it bring molecules and ancient rocks in contact with each other. Water may have been the first protocell.”

“And only in the liquid state, the ‘habitable zone’, is this possible. Only one place here and we’ve nearly run out.”

“How many oceans are there in the Solar System?”

I stared. “One.”

“No.”

“Surely you don’t mean the ancient Mars riverbed…”

“I mean currently.”

“I don’t follow.”

“Moons.” He rose up. “We need not be in a temperate zone to have an ocean, under the layers of ice. Europa, with its great ice sheet and ocean just beneath, powered by convective currents, like the primordial Earth ocean. Ganymede, explored by the Hubble Space Telescope, with a 100 mile deep ocean locked deep beneath the surface. Enceladus, with its outgassing plumes of water vapor. And even Titan, with its methane lakes. Not just water, but any liquid may yield the reactions we need.”

“So you’re saying that the gas giants we spotted in the data, farther out, may harbor miniature solar systems of their own?”

“It’s possible. Life is endlessly varied. And it is this flexibility that must keep us here.”

I stopped drinking my tea. “Here? What’s the point? Earth is dead.”

“It’s not dead yet. Dying, yes, but we have time to fix this. To find a new home for our people is why I’m here. It’s why you’re here. To leave this world with our kind is not our purpose.

“What are you saying? If WE find a new planet, then WE should get to live on it. There’s nothing for us here after that. We should be allowed to escape.”

“A part of us must escape. Our knowledge, our representatives of humanity reaching out to the Galaxy to embrace what is out there. But we must try to regain the homeworld.”

“I don’t understand.”

“We can only watch and imagine the future.” He stretched out his hand. “We cannot give up on our home, no matter how it punishes us.”

I batted the hand away and turned to leave.