Archive for October, 2010

Once Again with Feeling: The Planets of Gliese 581

Gliese 581 may be small as stars go, but it looms huge in the vision field of planetfinders.  As of late last week, measurements indicate the system has six planets of which three are Earth-size and -type, within the star’s habitable zone, with stable, near-circular orbits.

The Gliese 581 system has a persistent will-o-the-wisp quality.  Almost each of its planets (c, d, e and now g) has been pronounced in turn to pass the Goldilocks test, only to have expectations shrink when the data get analyzed further.  The first frisson of excitement arose when 581c was determined to be Earth-type, which quickened the usual speculations: atmosphere? water? life?  We don’t know yet and our current instruments cannot detect biosignatures at that distance (short of an unencrypted request for more Chuck Berry).  But there are some things we do know.

Gliese 581 is a red dwarf, a BY Draconis variable.  This makes it long-lived; on the minus side, it may produce flares and is known to emit X-rays.  Planets in its habitable zone are so close to it that they are tidally locked, always presenting the same face to their star.  The temperature differentials resulting from the lock imply hurricane-force winds and tsunami-like tides.  Gliese 581g, like 581c, is large enough to retain an atmosphere; the hope is that, unlike 581c or Venus, its specific circumstances have not resulted in a runaway greenhouse effect.

The real paradigm shift is the discovery that this solar system has many earth-size rocky planets, in contrast to the hot-Jupiter/hot-Neptune preponderance in most others.  The second enticing attribute of Gliese 581 is its relative closeness — a distance of merely 20 light years.  It is still millennia away by our present propulsion systems.  But I nurse the dream that if we see anything remotely resembling a biosignature, we will strive to reach it.  In the meantime, I suggest we give it a name that fires the imagination.  Perhaps Yemanjá, the Yoruba great orisha of the waters, in the hope that the sympathetic magic of the name will work.  Perhaps Kokopelli, the trickster piper of the American Southwest cultures, who may entice us thither.  I will conclude with the final words of my first article on Gliese 581:

“Whether Gliese 581c [g] is so hospitable that we could live there or so hostile that we could only visit it vicariously through robotic orbiters and rovers, if it harbors life — even bacterial life, often mistakenly labeled “simple” — the impact of such a discovery will exceed that of most other discoveries combined. Unless supremely advanced Kardashev III level aliens seeded the galaxy like the Hainish in Ursula Le Guin’s Ekumen, this life will be an independent genesis, enabling biologists to define which requirements for life are universal and which are parochial.

At this point, we cannot determine if Gliese 581c [g] has an atmosphere, let alone life. If it has non-technological life, without a doubt it will be so different that we may not recognize it. Nor is it a given, despite our fond dreaming in science fiction, that we will be able to communicate with it if it is sentient. In practical terms, a second life sample may exist much closer to home — on Mars, Europa, Titan or Enceladus. But those who are enthusiastic about this discovery articulate something beyond its potential seismic impact on biology and culture: the desire of humanity for companions among the sea of stars, a potent myth and an equally potent engine for exploration.”

Images: Top, comparison of the Sun and Gliese 581 habitable zones (the diagram is by Franck Selsis, Univ. of Bordeaux; the image of 581g was originally created for 581c by Ginny Keller); bottom, Kokopelli playing his flute.

Night and Day

“You go to the Caves of Winter. That is the Plan.”

“Winter, yes. The cold. Mother told us. And after the cold winter comes the warm. I remember. The winter will pass, won’t it? Why did she say, the winters grow? Teach me, Old One. . . .

~ “Love is the Plan, The Plan is Death” by James Tiptree, Jr.

Here in the Northern Hemisphere we are moving through autumn towards winter. That means the days are becoming shorter and the weather is getting cooler. The seasonal changes become more dramatic the further North you go; for people living near the Arctic Circle, the shortest day of the year – December 21st – will have nearly 24 continuous hours of darkness.

The change in seasons is due to the axial tilt of the Earth relative to its orbital plane (see image). In the summer, the sun is more directly overhead, which not only makes the days longer but the intensity of the sun’s rays are greater. It also means that the Southern Hemisphere experiences summer while the Northern Hemisphere is experiencing winger.

Seasonal changes on other planets in our solar vary considerably. Mars , with a similar axial tilt to Earth, has seasons that last roughly 6 months. Uranus has a much greater tilt and longer orbit has 20-year-long seasons with extremely variable weather. On Venus, on the other hand, the seasonal differences are pretty insignificant, since the planet has little axial tilt.

Not surprisingly, the change in the amount of daylight over the course of the year has had evolutionary consequences.   There are many plants and animals on Earth that have evolved to use day length as a cue for physiological changes that affect growth, reproduction and migration.

Plant reproduction, for example, is often dependent on having the right amount of darkness in a 24-hour period.  “Long day” plants – like soybeans and ryegrass – require fewer than a certain number of hours of darkness to flower, while “short day” plants – like spinach and coffee – won’t flower if there are too few hours are darkness. There are even “long-short-day” plants – like aloe – that require long days followed by short days to reproduce, and so only flower in the fall and “short-long-day” plants – like white clover – that flower in late spring. Disruption of the light-dark cycle can prevent such picky plants from reproducing.

Four Seasons - Fenner Nature CenterThe shortening of days in the fall also triggers changes in deciduous trees that helps them prepare for the cold of winter. The green chlorophyll in their leaves breaks down – unmasking already present yellow pigments – and is used to provide nutrients to the trunk and roots. Some trees also start making red pigments in their leaves, likely to help maximize the nutrients it can store for the cold winter months. Not only do these changes produce lovely fall color, but they also help trees survive until spring.

Animals are also affected by changes in day length. An extreme example is the Siberian hamster, which in the summer grows quickly and reproduce. As days grow short in the winter, the male hamsters’ testosterone levels drop, their testes shrink, and they store fat. Female Siberian hamsters go through similar changes.  While it’s not quite so dramatic in humans, we also respond to seasonal changes in daylight,  particularly with regard to our moods.

So how can these changes be used in science fiction? I think seasonal changes in day length are an often-overlooked aspect of realistic world-building.

While some science fiction stories include planets with extreme cold and hot “seasons”, these are often due to the unusual orbits of the planets. Examples of this are Hal Clement’s Abyormen and Brian Aldiss’s Helliconia*. Imagine a fictional planet that has an axial tilt similar or greater than Earth’s. The length of day should change with the seasons, and there should be indigenous life forms that have adapted to those changes, such as the creatures in Tiptree’s  short story “Love is the Plan, The Plan is Death”.

Day length is also plays a role when a planet is terraformed for human settlement. The Earthly plants and animals brought by the colonists would have to be specially selected (or engineered) so they are not adversely affected if the nights are significantly longer or shorter than Earth’s, or if the day length doesn’t change over the course of a year.

And imagine what might happen to life if the tilt of Earth’s axis were altered. Assuming any life survived such a dramatic event, it would have to adapt to changes in the seasons.

The cold grows, it grows, and your Mother-eyes are growing, glowing. Soon you will be alone with our children and the warm will come again.
Will you remember, my heartmate? Will you remember and tell them?
Tell them of the cold Leelyloo. Tell them of our love.

~ “Love is the Plan, The Plan is Death” by James Tiptree, Jr.

More reading:

Top Image: Diagram Earth and Sun from Wikipedia
Bottom Image: Four Seasons – Fenner Nature Center by Aunt Owwee, on Flickr

* Aldiss’s Helliconia may have has Earth-like seasons in on top of the centuries-long “seasons” due to its unusual orbit. It’s the latter changes that are the focus of the Helliconia novels.

Malaria-proof Mosquitoes?!?

This is some seriously cool shit. Entomologists and geneticists at the University of Arizona modified a single gene in the Anopheles stephensi mosquito in the hope of shortening its lifespan to the point where the malaria parasite would be unable to mature fully before the host died. Instead, they entirely blocked infection by Plasmodium falciparum, the primary human malaria parasite. They still don’t understand entirely why it worked (you can find the actual published data here), but by all accounts it sure seems to.

Malaria is one of those diseases that kills a million or so people each year, but because nearly all of those million people live in third-world countries not much gets done about it. Drug companies can’t make much profit from making a drug that only poor people would buy, so progress has been slow. In fact, most of the current efforts to fight malaria revolve around mosquito control rather than targeting the parasite. There’s some really cool research going on here at the University of Florida that revolves around designing pesticides that target the mosquitoes’ uniquely alkaline digestive system, theoretically leaving other insects, fish and humans (with our acidic digestive systems) unaffected.

But what good is this new Mutant Mosquito going to do, besides maybe inspiring the next SyFy channel original movie? It’s far too early to say anything for sure, but some of the articles I’ve read are excited about replacing wild mosquitoes with the mutant construct. This seems pretty unlikely to me, given that the mutation reduces the mosquito’s lifespan, and therefore its breeding window, by about 20%. That’s not going to compete successfully with the wild mosquitoes.

The other argument is the ‘What have we wrought?!?’ conundrum, which is what I really wanted to explore here. No one is seriously suggesting that we should introduce these new mosquitoes into the wild, but the potential to take a lab-created organism and replace an existing one with it is fraught with interesting moral and ethical questions.

First, can we really predict every possible outcome? What if something goes horribly wrong once the mosquitoes are released? Isn’t that what happened with the love bugs? Those stupid things are everywhere!

Ok, the story about the love bugs being created in a lab and accidentally released is amusing and all, but it’s a myth. We have for a reason.

Also, genetically modified crops have been in circulation for several years. A majority of transgenic crops are herbicide- or insect-resistant, but others are designed to be resistant to extreme weather conditions or specific viruses and parasites that are problematic for farmers. Some crops are even engineered to be nutritionally fortified and have been used to alleviate chronic malnutrition. There is still some controversy over the use of these crops, especially in regards to the effects on biodiversity and potential for the modified DNA to spread to other plants in unpredictable ways. These are real concerns. Only time can really tell what the long-term effects will be, but the metaphorical wheel is in motion. So far, the results are positive. Nothing has gone horribly wrong, and this technology honestly gives me a glimmer of hope for the future.

Plants are obviously not on the same scale as genetically modified insects, though. Insects can crawl and fly and spread themselves across the globe. Malaria isn’t the only disease spread by mosquitoes, either. West Nile Virus, Dengue Fever, Yellow Fever… it’s not difficult to imagine one of these monsters filling whatever gap was left by the elimination of malaria. Still, we have to look at the very real danger malaria presents. If replacing the wild mosquitoes with this construct was a viable option, would it be ethical not to do so? How do we weigh the million actual lives that are lost every year to this parasite against the potential harm it could cause? I don’t really have an answer to that, but I think it will be very interesting to watch the progress of transgenic crops in agriculture. Good or bad, the results of these forays into the genetic manipulation of our environment will likely set the precedent for the future.

This post is reprinted with the author’s permission.