El Cerrito Hillside Natural Area

Add:
American Coot
Sharp-shinned Hawk
Southern Alligator Lizard (Elgaria multicarinata)
Northern Mockingbird

Iris and I went for a very nice walk this morning. Iris found a couple of pellets (she thinks they are from an owl, I suspect they were regurgitated by a hawk) which contained the full skeleton of a pocket gopher and quite a lot of fur. We also found the partial skeleton, including the skull, of a dear. The highlight was when we came around a corner and a Red-Tailed Hawk Came running out from the bushes. It took off but circled low over us such that it was clear it did not want to leave the spot. I checked the bush it had come out from under and found a freshly killed and partly dismembered American Coot. Continuing a little way along the path we came to a swampy area and a free flowing creek that could easily be coot habitat. We left the coot for the hawk to finish off.
Iris is getting good at using binoculars, and we spent a while sitting and looking at Scrub-Jays, Spotted Towhees and hummingbirds to give her practice. Found a small (~10cm) Southern Alligator Lizard under a chunk of wood in a field. When I let it go it ran down a gopher hole. On our way back to the house, we passed a Northern Mockingbird on the edge of the park and I heard a Sharp-shinned Hawk calling.

El Cerrito Hillside Natural Area

Add:
Dark-eyed Junco
American Goldfinch

More on Europa's Ocean

Let's start with a simple calculation. The mean radius of Europa has been estimated at 1,560.8 km. The mean depth of the ocean has been estimated at 100km. Earth's ocean by comparison has a mean depth of 4 km, but covers a much bigger sphere. How do the volumes of these two bodies of water compare?

Volume of Europa=(4/3)*3.14*(1,560.8^3)=1.59×10^10
Volume of Europa excluding outer 100KM of water= (4/3)*3.14*(1,460.8^3)= 1.30×10^10

Volume of Europa's water=1.6×10^10- 1.3×10^10= roughly 2.8 billion cubic kilometers of water.

The volume of earth's oceans is estimated at 1.3 billion cubic kilometers.

So Europa hypothetically has about twice as much liquid water by volume as earth. So a big ocean.

Now let's think for a minute about that ocean. 100,000 meters deep. The gravity on Europa is a gentle .134g, so I'm guessing the water pressure 100K down is similar to that on earth 13,000 meters down. Deeper than the earth's ocean actually gets, but comparable to the pressure at the bottom of the Marianas Trench, something over 1000 atmospheres.

The bottom is important when thinking about life, because unlike earth, where most of the life lives on the surface, where the light is, on Europa the proposed energy source is hydrothermal vents, on the bottom. There are lots of ramifications to this. One, as I discussed before, hydrothermal vents are unlikely to produce enough usable energy to keep a whole ocean twice the size of Earth's own filled with life. Life will live where the energy is, as close to the vents as can be tolerated.
Second, unlike on Earth where there is serious stratification of the oceans because the top is warm and the bottom is cold, on Europa, the heat comes from below. Hot water rises, and cold water sinks. If you heat a pot of water from below, you quickly get powerful convection currents roiling the waters. Europa likely has powerful upwellings, downwellings, sidewellings and so on. Then, once you have all that motion on a rotating body, you get the Coriolis effect which leads to such things as cyclones, whirlpools and gyres. Add to that tides from interactions with Jupiter and the other moons, and all that water isn't just sitting still down there under the ice. It is racing too and fro and hither and yon. Which makes possible another type of energy collection on Europa; windmills (or hydro electric, or something such). Anchor yourself to ground or ice, let the water swirl by you and allow it to turn some part of you. Use that energy to fix carbon (or something) and you are an autotroph. Then other Europans can come along and eat you, and you are supporting a community, without relying on chemicals from the vents.

I admit it is a bit far fetched, but it is the only way I can think of to support life away from the hydrothermal vents in Europa's ocean. Thoughts?

El Cerrito Hillside Natural Area

Add:
Red Breasted Nuthatch
Downy Woodpecker

El Cerrito Hillside Natural Area

Add:
Hermit Thrush
White-crowned Sparrow
Golden-crowned Sparrow
Spotted Towhee
House Finch

Musings on the Oceans of Europa

In the sequels to Arthur C. Clarke's "2001, A Space Odyssey" humans discover, and are told to not interfere with, life forms on Europa, the watery moon of Jupiter. Europa is thought to have some tens of kilometer of water ice over (potentially) 100 kilometer of liquid water, with a rocky core that is kept at least partially molten by the stretching and straining caused by the tidal pull of nearby Jupiter, around which it zips every 3.55 days.

It is thought quite possible that the ocean bottom of Europa, as the ocean bottom of earth, could have hydrothermal vents, and as on earth, these vents could potentially support life. On earth, ecosystems around the vents rely on chemosythesis (the production of energy bearing organic compounds by the oxidation of high energy chemicals, in this case hydrogen sulfide) rather than photosynthesis.

A wide range of methods have been proposed for testing the hypothesis that their are lifeforms in the waters of Europa, from biological testing of the waters to robotic submarines to a search for freeze dried lifeforms orbiting near Europa, thrown off into space by collisions with other bodies.

All of these seem like long shots to me, even assuming there is life there to find. Hydrothermal vent lifeforms on earth do not venture far from the vents. The concentration of hydrogen sulfide drops off rapidly as one moves away from the vents. It is likely that a Europan ecosystem based around hydrothermal vents would be very localized, soaking up every scrap of whatever the chemical was that fueled their physiology. Just as there is very little sunlight reaching the dirt in a mature forest, very little of the chemical energy source would likely escape beyond the immediate surroundings of the vents. The autotrophs would be in tight knots around each vent, and the heterotrophs would tend to follow. Unlike our oceans, in which the entire surface is covered with a sheen of plankton, the top of Europa's waters would likely be dead.

This line of thinking points to two other proposed methods of looking for life. One is to map out beforehand where the hydrothermal vents are, and send a probe directly there. This may be doable, if we can use magnetic and gravitational data to map the plates and faults of Europa's rocky interior's crust, and predict the mostly likely spots.

Perhaps simpler as a first step would be to look for the breakdown products of chemosynthesis in the waters. Just as the earliest sign distant aliens would have had of life on earth was the buildup of excessive oxygen in our atmosphere as a byproduct of photosynthesis, perhaps the easiest way to tell if there are Europans is to look for their waste gases.
This of course, is made more difficult that we have no idea what chemicals they would use as an energy source, or how they would process it. We would basically be looking for any sort of surprising chemical imbalance, with the assumption that we can thermodynamically predict what a balance should look like.

Of course bringing back a Europan in a jar would be much more exciting than saying, " we have a significant deviation from our predicted chemical balance." But checking the chemical balance is probably a lot more doable as a first step.

Writers' Strike

It seems to me that economists should be able to quantify the value of the work of a profession to society based on the larger societal impacts of that group temporarily ceasing their work. We'll call this variable V(s). In France, when the transit workers go on strike the nation is temporarily paralyzed. High V(s). If the New York City police department went on strike, serious trouble. They have a high V(s). I hear that the Screen Writer's Guild has been on strike for a while now. Is anyone outside of LA missing them? V(s)=?

More Birds for the Hillside Natural Area

Iris and I went out for a walk in the EC Hillside Natural Area from 9-9:30AM. I forgot to bring my binoculars, so was mostly birding by ear. I can add the following birds to the list for the park:

Red-shafted Flicker
Red-breasted Sap-Sucker
American Robin
Black Towhee
Bush Tit
Mourning Dove

El Cerrito Hillside Natural Area

I've decided to compile a list of vertebrates occurring in El Cerrito Hillside Natural Area. More specifically, in the smaller northern section of the park that is directly behind my house.


View Larger Map

I may expand to the whole Natural Area once my mobility increases.

This afternoon, I took a short walk in the park from 1:15-1:40.

I saw or heard the following birds:
Western Scrub-Jay
Stellar's Jay
American Crow
Northern Raven
Yellow Rumped Warblers
Bewick's Wren
Chestnut-backed CHickadee
House Sparrow
Ruby-Crowned Kinglet
Anna's Hummingbird
Turkey Vulture
Red Tailed Hawk

UPDATE:
(Added 12/9/07)
Red-shafted Flicker
Red-breasted Sap-Sucker
American Robin
Black Towhee
Bush Tit
Mourning Dove

(Added 12/11/07)
Hermit Thrush
White-crowned Sparrow
Golden-crowned Sparrow
Spotted Towhee
House Finch

(Added 12/12/07)
Red-breasted Nuthatch
Downy Woodpecker

(Added 12/14)
Dark-eyed Junco
American Goldfinch

(Added 12/16)
American Coot
Sharp-shinned Hawk
Northern Mockingbird


I saw, or sign of the following mammals:
Eastern Fox Squirrel (Sciurus niger)
Mule Dear (Odocoileus hemionus)
Voles (Microtus californicus? runways and burrows)
Pocket Gophers (burrows)
Fox (Grey fox? scat)

I didn't see any herps or fish.
(Added 12/16)
Southern Alligator Lizard (Elgaria multicarinata)

Nothing unusual so far. I will add more as I see it.

SAD, Photoinducability, Skeleton Photoperiods, and the Winter Festivals of Lights.

Seasonal Affective Disorder, generally known as SAD, or winter depression, is the most noticeable expression in humans of photoinducability, the changing of physiology or behavior by day length (or more particularly, photoperiod, the number of hours of light in a day). Sufferers of SAD, which have occasionally included myself, are generally in good mental health much of the year, but if photoperiod gets too short, they find themselves depressed. When photoperiod increases again, the depression recedes. In Alaska, where days can get very short for extended periods, about a tenth of the population suffers from clinically significant SAD.

That much is general knowledge. It is also widely known that many other species use photoperiod to time many aspects of the biology, including breeding, migration, food choice and hibernation. If the days are getting long, it is time for breeding, or whatever else one does in the spring. If they are getting very short, it is time for winter activities, such as sleeping in one's hole. Photoperiod, and the change therein, is a highly predictable indicator of what day of the year it is at any particular location.

This week, in a lecture by Dr. George Bentley, I learned a bit about how animals measure photoperiod, and this changed my thinking about SAD and the winter festival of lights that appears as so many different holidays in so many different religions.

One can imagine various methods an animal's brain could use to figure out how long the day is. An animal could have a solar powered kitchen timer in its brain. Sun comes up, timer starts. Sun goes down, timer stops. Where the timer stops is how long the day was. But there are problems with this model. For example, what if an animal goes in its burrow for much of a day? The timer would stop running. Another model, and one that seems to be what many animals do, is to have a timer that also started running at dawn, but doesn't stop every time the animal is in the dark. This timer measures the distance between dawn, the first light the animal sees that day, and dusk, or the last bright light the animals sees that day.

The ramifications of this are not immediately obvious until you hear how can be used. Animals in the lab are often kept in specific light:dark schedules (12:12 or 14:10) to see what happens to their physiology or behavior under different light regimes. In many species, when photoperiod is increased, the animal responds as though it is spring, building bigger gonads and such. But because the animal's physiology is not actually measuring the number of hours of light, but the number of hours between first light and last light, one can induce the same effect using what is called a skeleton photoperiod. A one second flash of light at 5AM and another at 7PM, with total darkness the rest of the day, is 14 hours between first light and last light. Move hamsters into these conditions, and their gonads start growing, as thought they had had 14 continuous hours of light.

After the lecture, I asked Dr. Bentley if anyone had tried a skeleton photoperiod on human volunteers, to see if it would be effective in combating SAD and similar conditions. If the human brain could be tricked into thinking the days were long by a properly timed, but short and convenient, blast of light late in the day, this would be both extremely useful and biologically fascinating. He said that while SAD was often treated with light therapy, he was not aware of any study looking at whether a short exposure to light carefully timed late in the day could have any effect. Then someone walked by, in the hallway and said to someone else, "Happy Hanukkah, are you going to light a candle tonight?"

I think you see where I am going with this. Hanukkah candles are traditionally lit an hour or two after sundown, when it has become truly dark out. In many parts of the world, Jerusalem say, this equates to 12 to 13 hours after dawn. Celebrants are directed to meditate on the candles, and the joy of Hannukah. The traditional candles burn out after about a half hour.

Festivals this time of year often involve fixating on lights in dark evenings. Hinduism, Sikhism, Jainism, Christianity, the Persians, the Chinese, the old Germanic and Norse tribes and so on all had comparable winter festivals of light. Of course it has long been thought that the winter holidays are a great way to fight the winter "blahs" with light. Cheerful light. Evening light. Photoinducing, skeleton photoperiodic light?

In clinical trials of current treatments for SAD, an hour or so of very bright light at almost any time of day has a significant ameliorative effect, among those who stick with it. But many patients drop out, citing the inconvenience and boredom of sitting and staring toward (but not directly at) a big lamp for an hour a day. I can't help but wonder if the festivals of lights point to a better way, not only making the exposure to light a celebration rather than a chore, but also giving guidance as to what time of day to observe those lights and fixate on them. Do it in the early evening, when dusk would be in the summer, and maybe, just maybe, you make some part of your brain think it is summer.

Light regime change begins at home.