The current Carnival of Space is up at OrbitalHub, with a lively take on habitable planets from Charles Magee’s Lounge of the Lab Lemming. Magee, now a field geologist in central Australia, once operated a laboratory that analyzed crystalline and glassy solids — ‘everything from dead people to bits of the Moon,’ as Charles puts it — but he brings his analytical skills to bear this week on a much more theoretical problem: How much is a planet worth?
Greg Laughlin (UC-Santa Cruz) has been kicking the question around on his systemic site, creating a prize for the first planet to reach a million dollars in value on his scale, with Earth setting the baseline at four quadrillion. Mars weighs in at a mere $13,988 on this scale, yet no known exoplanet even comes near that disappointing valuation. Magee has fun with Greg’s equations and goes to work on Venus, focusing on its albedo. Assuming a terrestrial albedo (0.36), he quickly arrives at a Venusian temperature not dissimilar from the current weather near his home in Canberra, some 20 degrees Celsius.
But there’s always a catch:
Of course, pedantic observers may note that Venus’s blackbody behavior is tempered by the fact that the planet has a thick atmosphere, which warms the surface via the greenhouse effect. We can calculate this second order effect by substituting Teff (the model blackbody temperature — 230-330K depending on albedo) with Treal, the actual surface temperature of 737K. This drops the valuation from 1440 trillion dollars to 2.9×10-89 dollars, or 2.9×10-87 cents. But in the current financial environment, a mere 104 order of magnitude decrease is not a problem. Rather, it is a badge of honor. Who wouldn’t want ten thousand googles in times like these? Were I an investment manager instead of a geologist, I could use that as a justification for a million dollar bonus paid by congressional bailout.
Ouch. Not that there are many better bets in the Solar System, with Titan weighing in at 9.5X10-44 dollars, or our own Moon at 7X10-25 dollars. Yet Greg has a defense of the Venusian breakdown:
Point taken! I’m not sure though, that a top-dollar Venus necessarily points to a flaw. The valuations are a quantitative measure of potential for a planet to be habitable, given only bulk physical properties currently measurable across light years of space. One is still faced with the quandry of whether to invest in to finding out whether a given planet measures up. If Venus were sheathed in water clouds rather than sulfur dioxide clouds, it would quite possibly achieve its potential as a quadrillion-dollar world.
Among exoplanets, the Laughlin payscale isn’t kind to Gliese 581c, the world that provoked a boomlet in habitable planet speculation not so long ago. Laughlin’s methods bring in a value of $158.32. ‘Potentially habitable’ is not the same thing as ‘habitable,’ of course, but it’s interesting to see that Laughlin believes the first planet to fit the former description will likely be discovered within the next year using radial velocity methods from the ground. His formula for calculating its value is worth reading about.
All this is great fun. Ponder this: The US paid $15 million for the Louisiana Territory in 1803. As Laughlin notes, it’s a figure that works out to $750 million in today’s currency. The cost of the Kepler mission is roughly $600 million, a comparable figure. While the Louisiana purchase brought in two million square miles (one percent of Earth’s square mile total surface), Kepler may discover on the order of 100 terrestrial planets. How much is such a world worth? Hint: A habitable Alpha Cen Bb (not in Kepler’s field of view) clocks in at $6.4 billion.
But back to the Carnival: Ethan Siegel looks at Govert Schilling’s The Hunt for Planet X: New Worlds and the Fate of Pluto (Springer, 2008), an account of the unfolding discovery of the outer Solar System (I’ve had this one on my desk for some time and keep intending to get to it, but it’s quickly making its way to the top of the stack — more later). Also, don’t miss Nancy Atkinson’s Universe Today interview with John Mather, discussing the James Webb Space Telescope, where it’s been and where it’s going. JWST’s infrared views of Kepler-identified terrestrial worlds should provide much useful information, hopefully enough to clarify the difference between blue chip performers and toxic assets.