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Further reading on aliens

December 17, 2012 By

Cover courtesy of Goodreads.

Confession time: My space-opera WIP has aliens, and the task of writing them well daunts me. There’s a balance between creating a non-human character who is both alien and yet relatable to human readers, and I don’t want to mess it up. I don’t want my aliens to be humans in funny suits. And yet, the entire conceit, the central what-if question that makes me want to tell this story, revolves around aliens. The aliens aren’t going anywhere. So I’ve been doing research.

I was impressed by David Brin’s eight, very distinct sapient species in Brightness Reef. I’ve also heard that C.J. Cherryh does a wonderful alien, and I intend to read Foreigner very soon. On the nonfiction side, I picked up Stanley Schmidt’s Aliens and Alien Societies for some tips.

The book was a decent overview, and I managed to pull together a further-reading list from the bibliography, based off my interests. It looks like I need to find a way to acquire back issues of Analog. [update: Mwahaha the University library has access to the e-journal. I am set!]

On Reproduction (p. 93)

Two sexes are enough to confer large evolutionary advantages, but some evolutionary lines may have more … On the other hand, some Earthly animals evolved from sexual ancestors have found ways to reproduce parthenogenetically–there are entire species of lizards whose members are all identical females.

My main alien character is female, but I pondered sex and pronouns quite a bit, and out of general interest I want to check out this article:

  • Cueller, O., “Animal Parthenogenesis,” Science, Aug 26, 1977

On Really Big Civilizations (p. 131-135)

In addition to aliens, I’m using hyperspace to get my characters from point A to point B, with permanent jump stations modeled after Lois McMaster Bujold’s Vorkosigan Saga: each gate leads to a specific destination and you need a spaceship to go through it. Clearly, I have a strong interest in interstellar travel.

  • Zubrin, Robert M., “The Magnetic Sail,” Analog, May 1992.
  • Arnold, Roger, and Donald Kingsbury, “The Spaceport,” Analog, Nov/Dec 1979.
  • Barlowe, Meacham, and Summers, Barlowe’s Guide to Extraterrestrials, Workman, 1979.
  • Mallove and Matloff’s The Starflight Handbook, Wiley, 1989.
  • Forward, Robert L., “Faster Than Light,” Analog, March 1995.

On religions and sciences (p. 114-117)

It seems fairly safe to say, though, that most [human] religions include rituals related to a belief in one or more powers higher than human, stories to explain the origins of world and life, and teachings aimed at inculcating and perpetuating a model code.

Good reminder! I need to do more worldbuilding on my alien religion.

On trade (p. 119-120)

  • Salomon, Warren, “The economics of interstellar commerce,” Analog, May 1989.
  • Barnes, John, “How to build a future,” Analog, March, 1990.

On custom, etiquette, social pressure, morality (p. 122-123)

Many social dictates of acceptable behavior involve such areas as reproduction (a society must control fighting over potential mates, ensure that children are raised acceptably, and so forth), eating and elimination … To make alien cultures live and breathe, you will want to give ample attention to details of custom, gesture, morality, and clothing; and you will want all of these things to grow out of your particular aliens’ nature and background.”

Schmidt recommends the novels of C.J. Cherryh for her skillful use of gesture and nuance to distinguish alien from human and alien from alien. On a related note, author N.K. Jemison recently wrote a blog post on worldbuilding and profanity.

What are your favorite aliens in fiction?

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Freezing your butt off on Barsoom

May 2, 2012 By

Greetings from week 4 of planetary atmospheres! Last week, we discussed the proposed Titan Mare Explorer mission to the methane seas of Titan, and I’ll admit I’m a little sad to see this one go. There’s something so delightful about nautical expeditions on other planets. For the follow-up act, this week’s topic is world-building climate from first principles.

Habitable Zone – the region around a star where an Earth-like planet can maintain liquid water on its surface.” ~ Virtual Planetary Laboratory

It sounds so binary, doesn’t it? Either you’re in or you’re out.

To first order, planetary climates are defined by their orbits around the local star, and the luminosity of that star. The brighter the star, the farther the habitable zone is from it. However the effect of the insulating atmosphere is also hugely important. Good old Earth, for instance, would have a globally-averaged temperature of -18°C (0°F) without the greenhouse effect provided by gases in the atmosphere. Notice that’s below the freezing point of water. Slap an atmosphere on us, and you get a balmy 15°C (59°F), which (trivia alert!) is also the annually-averaged temperature of Rome and Melbourne. The greenhouse effect (not to be confused with global warming, please) gives us a planet I’m happy to call home. Without it, not so much.

In fact, I think I prefer this definition of habitable zone from Wikipedia, because it emphasizes the role of the atmosphere:

In astronomy and astrobiology, the habitable zone is the region around a star where a planet with sufficient atmospheric pressure can maintain liquid water on its surface.” (emphasis mine)

The two largest controls on planet habitability are the orbit of the planet and the greenhouse effect of the atmosphere, which warms the surface and moderates the climate. Even with an atmosphere, things can get complicated for life–say if nighttime temperatures are 60°C colder than daytime, or if the planet is tidally-locked such that only one side is the sunny side. To explore some of these nuances, let’s start by assuming a planet (with an atmosphere) that can sustain liquid water on the surface. What other factors should we consider for world building our science fictional setting?

Eccentricity

Eccentricity refers to how circular the planet’s elliptical orbit is around the sun. Earth’s orbit is pretty circular, and the variation in distance from the sun over the year only leads to a 1% change in atmospheric (not surface) temperature. On Mars, on the other hand, the eccentricity of orbit produces a 10% variation in atmospheric temperature. This variation strongly affects seasons on Mars.

Tilt

Aha! But seasons on Earth are not due to eccentricity, they are caused by the tilt, or obliquity, of the Earth’s rotation axis. In other words, summer happens NOT when the Earth as a whole is closest to the sun, but when your hemisphere is pointed at the sun. Likewise winter occurs when your hemisphere is pointed away away from the sun.

Precession

Today the Earth’s rotation axis (i.e. North Pole) points at Polaris. But in 3000 BC Thuban in the constellation Draco was the north star, in 320 BC Greek navigator Pytheas described the celestial pole as star-free, and in AD 3000 Alrai will be the north star. Vega, the second brightest star in the northern hemisphere was the north star in 12,000 BC and will be again in 14,000 BC.

All of which is to say, planets can behave as wobbly tops. In the case of Earth, this orbital parameter only affects climate on a 20,000 year cycle (so, Ice Ages), but I like to include it because it’s neat to think of the north star as something that’s not fixed. Taken together, changes in eccentricity, tilt, and precession define the Milankovich Theory of the Ice Ages. Milutin Milankovich was a really humble guy, as epitomized in this quote: “I do not consider it my duty to give an elementary education to the ignorant, and I have also never tried to force others to apply my theory, with which no one could find fault.” (It’s a pretty good theory but it’s not perfect, and it has been improved upon.)

Daily temperature range

Here’s where it starts to get interesting. The daily temperature range of a planet depends on the following: solar flux of energy impinging on the planet; planetary albedo, or reflectivity; gravitational acceleration; atmospheric pressure; and specific heat, or how much energy it takes to change the temperature. The latter two depend on atmospheric composition, and bring about a temperature lag as the planet spins from sunlight to darkness. If the heating is sluggish, then the climate of the entire spheroid is fairly temperate. But if the heating is rapid, then so to is the nighttime cooling. Brrr. Plugging in standard numbers for Earth and Mars (with its thin atmosphere), we see a daily temperature range of 2°C on Earth and 80°C on Mars. Now remember these exact numbers are valid for a level pretty high up in the atmosphere, not the surface–but they control the surface temperature, and clearly there’s huge swing between daytime highs and nighttime lows on Mars, in addition to its strong seasonality. The atmosphere of Mars is a crummy blanket.

Fortunately, writers get to play god and set things up just so. Though for all the prevalence of terraforming stories, I don’t see as much focus on atmos-forming, with the exception of climate-controlled domes, I suppose. And of course, I’ve skipped over the issue of atmospheric make-up entirely, but it’s important to keep in mind. For instance Mars is 95% carbon dioxide; humans and animals can’t breathe it without a feat of engineering … Of course, biology produces/requires oxygen, so these aren’t mutually exclusive. Though I do wonder about the timescales of terraforming a breathable atmosphere, and I hope to return to this topic in a future post.

Something I find really interesting, but it’s not my area of expertise, is imagining how photosynthesis would operate on planets with crazy orbital mechanisms. For instance, what kind of plant life would evolve on a planet that rotates very slowly, with long periods of night and long periods of day. Any ideas?

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Sail away on a methane sea

April 25, 2012 By

Greetings from Week 3 of planetary atmospheres! Last week, we discussed exotic cloud types on so-called Hot Jupiter exoplanets, the challenges for liquid water on Mars, and how to estimate winds from satellite imagery. This week, it’s all about liquid hydrocarbons on Titan.

Titan Saturn

Concept art of Titan's surface (artwork by Craig Attebery)

Titan is the largest moon of Saturn and, like Earth, its atmosphere is dominated by nitrogen. Also like Earth, it has a hydrological cycle involving rain, clouds, rivers, and lakes–though in the case of Titan, we get methane rain rather than water rain. The topography of Titan, as gathered by the Huygens probe, is characterized by extensive dried-out channel networks that provide evidence for past flood events. And hydrocarbon lakes have been observed at high latitudes!

A mission to land a “boat” on one of the methane lakes of Titan is currently under review by NASA.

(As a HUGE aside, I recently read a story in which the characters–who live in a green, lush forest–believed that oceans no longer exist. I find this very frustrating. If it rains that means there’s a hydrological cycle, and the water has to come from somewhere. If it rains a lot, then there needs to be a large source of water, like an ocean. I get that in post-apocalyptic societies, much knowledge is lost. But this still feels like idiot plotting to me.)

Hydrocarbon lakes on Titan (Image credit: NASA/JPL/GSFC)

The target for the first extraterrestrial sea exploration is Ligeia Mare, which is larger than Lake Superior. The backup target is Kraken Mare (awesome name, no?). The Titan Mare Explorer (TiME) is proposed to launch in 2012 and splashdown on Titan in 2023 for a 7-year cruise. The scientific objectives are the following:

Titan Mare Explorer TiME

Concept art of Titan Mare Explorer (Image Credit: The Johns Hopkins University Applied Physics Laboratory/Lockheed Martin)

  • Determine the chemistry of a Titan sea
  • Determine the depth of a Titan sea
  • Constrain marine processes on Titan
  • Determine how the local meteorology over the sea varies on diurnal timescales
  • Characterize the atmosphere above the sea

I think I might have a crush on Titan. Or maybe it’s the inherent romance of a sea voyage under a Saturn-filled sky. The mash-up of the familiar with the alien gives me shivers. Out of all the planetary atmospheres I’ve studied so far, Titan has the most obvious similarities to Earth from a weather perspective. Though, you know, METHANE. Ligeia Mare might look like a gigantic oil slick.

In podcast-listening news, two stories jumped out at me recently, both on Escape Pod. “Asteroid Monte” by Craig DeLancey was a thoroughly enjoyable space-adventure/buddy-cop story with aliens. Also, the narration by Rajan Khanna really shone. And “‘Run,’ Bakri Says” by Ferrett Steinmetz, with its brilliantly ratcheted tension, in which a girl becomes a terrorist while stuck in a time loop to save her idiot brother. I enjoyed the parallels drawn to video games, and I haven’t been able to stop thinking about this story. Go check them out.

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Now with Hot Jupiters

April 11, 2012 By

This post picks up the second week following my coursework in planetary atmospheres. Last week, we discussed the lack of an ozone layer on Mars, extremely high levels of incident UV (ultraviolet) radiation at the surface, and Mount Everest-sized dust devils.

Fun Fact #1: How to get a space-based estimate of wind speed on other planets.

On Earth, gravity waves form in the lee of air-flow barriers, such as mountains. Air rises in the peak of each wave and a cloud may condense, whereas the trough remains cloud free, forming a distinctive pattern:

South Sandwich Islands lee waves

Wave clouds downstream of the South Sandwich Islands (NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center)

Wave clouds over Ireland

Wave clouds over Ireland (Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC)

The Viking Orbiter mission discovered similar cloud features forming in the lee of crater rims on Mars.

Wave clouds on Mars

Wave clouds on Mars, as captured by the Viking Orbiter

These gravity waves, which are highlighted by the clouds, have a characteristic equation defining their shape: A parcel of air displaced by a barrier will oscillate according to the Brunt-Väisälä frequency. The oscillations are damped for a very stable atmosphere, and vigorous for a less stable atmosphere; in other words the frequency is a function of the gas composition and temperature structure of the atmosphere, which can be observed remotely. Likewise, we can observe the wavelength of the lee wave clouds from remote images (see image to left). Since velocity is simply the product of frequency and wavelength, voilà, we have an estimate of wind speed.

Fun Fact #2: A dearth of liquid water on Mars, or why canals are a bad idea.

Theoretically, there exists a range within typical Martian surface pressures and temperatures at which pure liquid water is stable against boiling. This is because the condition for boiling depends on the total atmospheric pressure, which is sufficiently high on Mars. However liquid water is unstable to evaporation, because evaporation instead depends on the partial pressure of the water vapor in the air. Since the modern atmosphere of Mars is so dry, evaporation is really efficient. This vigorous evaporation leads to cooling and the formation of ice. In practice the ice sublimates (goes straight from solid to vapor phase) as the seasons progress from winter to summer, without ever existing as liquid, though in theory the addition of salts could depress the freezing point sufficiently for liquid brine to occur.

This same logic explains why we observe CO2 polar caps on Mars but not Antarctica, even though the pressures and temperatures are in the right range. The partial pressure of vapor phase CO2 is low on Earth and high on Mars–high enough to condense at the Martian poles.

Fun Fact #3: Liquid iron and silicate (rock vapor) clouds on Hot Jupiters.

Hot Jupiters are a class of exoplanet that can have way more exotic clouds than the boring old H2O, CO2, and methane clouds observed in our solar system. The most famous Hot Jupiter is 51 Pegasi b, nicknamed Bellerophon. What sends me in a tizzy, as a climate dynamicist, is imagining the effect of dark-colored clouds on the planetary energy budget. The fact that the clouds on Earth are white has a huge role in controlling surface temperature. How would climate dynamics play out with clouds made of liquid iron?

Hot Jupiter Osiris

Concept art of gas-giant planet HD 209458b nicknamed "Osiris" (image courtesy of NASA)

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In it for the exoplanets

April 4, 2012 By

As I mentioned on the blog last week, I am taking an actual class this quarter, Planetary Atmospheres. We’ll be covering Earth, Venus, Mars, Titan, Jupiter, Saturn, Uranus, Neptune … and exoplanets! Atmospheric dynamics of exoplanets is just plain rad, and it’s a nice change to focus on a topic that’s relatively irrelevant to human society and is unequivocally awesome. (Most of my research focuses on climate dynamics under global warming scenarios, so both relevant and unfortunately equivocal in the eyes of the general public.)

In the spirit of science geekery, I’d like to share a few of the tidbits I picked up in Week 1, of course focusing on the fun facts over tedious mathematical derivations that tend to crop up in a graduate-level astronomy/atmospheric sciences class.

Fun Fact #1: The tropopause occurs at nearly the same pressure level on all planets!

The tropopause is the boundary separating the lowest layer in the atmosphere, the troposphere (where weather happens) from the next layer up, the stratosphere; this boundary also marks a cold point in the profile of atmospheric temperature. The commonality of tropopause level is super surprising because the structure and gas composition of planetary atmospheres vary widely (say Earth compared to Jupiter)–but the minimum temperature always occurs at approximately 0.1 bar! Scientists are investigating this feature, and suspect it’s somehow related to pressure broadening. Pressure broadening is an increase in the absorption spectra of a molecule due to collisions with other molecules. Basically it means that a gas layer, such as the ozone layer in the Earth’s stratosphere, can absorb more solar radiation (and hence warm the air) BECAUSE it’s a layer of many molecules, compared to a molecule hanging out by itself. But what sets the level where ozone on Earth or methane on Titan wants to hang out and absorb UV?

Mars Dust devil

Image credit: NASA/JPL-Caltech/Univ. of Arizona

Fun Fact #2: Condensational heating: Not just for H2O.

On Earth, water vapor condenses to rain. On Mars, there’s evidence of precipitable solid-state CO2, or CO2 “snow”. Methane rain on Titan, etc. This has implications for convection, because condensation drives heating (called “latent heating”) and hence an increase in buoyancy of an air parcel. Strong convection on Mars (driven largely by strong surface heating though latent heating contributes) is how you get the Mount Everest-size dust devils observed on the surface.

Fun Fact #3: The surface of Mars is sterilized daily due to insufficient ozone (i.e. sucks to live there).

Ozone: Good up high, bad down low. Ozone at the surface is pollution (referred to as L.A. type smog in textbooks), and causes a number of public health issues. Ozone up high protects the surface from incoming ultraviolet radiation, and is the reason why the (now recovering!) ozone hole over Antarctica was of concern and likewise why Australians wear hats.

Mars has only 0.3% of the ozone on Earth. However Mars is also farther from the sun, and receives less incoming ultraviolet radiation. How much less? Well Mars is 50% farther away from the sun than Earth, and following the inverse square law, this means it gets 44% of the incoming solar radiation, compared to Earth. In other words, the fact that Mars is farther from the sun doesn’t compensate for the lack of ozone. The result is that less radiation is absorbed in the atmosphere and can instead reach the Martian surface at wavelengths short enough to break carbon bonds–bad news for life.

So what do you think? Would anyone be interested in future posts following my adventures in Planetary Atmospheres?

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