Go Stargazing! July Edition

During July, you can watch a great planet race, as Venus closes in on Mars while they both close in on Saturn!

Saturn is now in the south southwest at dusk.  Look just to the west of due south, about 2/3 of the way up from the horizon to the zenith.

Venus remains high in the evening sky during July.  Face west at dusk and look for a point of light that outshines everything in the sky but the Sun and the Moon.

Mars is also in the western sky.  Look in the west at dusk for a reddish point of light between Venus and Saturn.

Observe all three carefully throughout July and watch as they get closer together.  By July 31, Mars will have caught up to Saturn, with Venus only about 7.5 degrees away.  Keep watching next month as Mars moves ahead of Saturn and Venus passes them both.

Jupiter is in the south at dawn this month.  It outshines all stars in the sky, so it’s easy to find.  By July 31, Jupiter rises at about 11 p.m.; it will be a late evening object next month.

In the west, a distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle are to its upper left; they mark Leo’s hindquarters.  This month, the Lion serves as the backdrop for the great planet race described above.  The Big Dipper is high in the northwest at dusk. You can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica.’  These stars high in the west and southwest, respectively, by dusk tonight.  Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see in all of July.

In the east, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair.   This triangle is up all night long in July, hence its name.  Scorpius, the Scorpion, is in the southeast at dusk.  Sagittarius, the Archer, known for its ‘teapot’ asterism, is to its left.  Between these two star patterns is the center of our Milky Way—the brightest part of that band as wee see it.  On a cloudless night far from the big city, see if you notice the Milky Way glow near the ‘teapot’ of Sagittarius.

Summer Triangle

Moon Phases in July 2010:

Last Quarter                       July 4, 9:36 am

New Moon                            July 11, 2:40 pm

1st Quarter                         July 18, 5:11 am

Full Moon                            July 25, 8:36 pm

Flag of Turkey
Creative Commons License photo credit: steelight

The new moon of Sunday, July 11, will align precisely with the sun and Earth, casting its shadow on the Earth.  This will cause a total solar eclipse.

Unfortunately, the shadow’s path is entirely over the South Pacific Ocean.  Easter Island and certain islands of French Polynesia are the only land where totality can be seen.  Even partial phases are visible only from South America.

On Tuesday, July 6, Earth is as far from the sun as it will get this year, a position called aphelion.  Remember, the Earth’s orbit is not quite a circle but an ellipse.  We are therefore slightly closer to the Sun in January than in July.  Also, remember that the difference between our January and July distances from the Sun is small.  When it comes to making us hotter or colder, the effect of our axial tilt dominates.

What a Croc!

Today’s guest blogger is Neal Immega. He has a Ph.D. in Paleontology and is a Master Docent here at HMNS. In his post below – originally printed in the Museum’s volunteer newsletter– Neal discusses the Geosaurus, a fossil featured in our exhibition Archaeopteryx: Icon of Evolution.

The Houston Museum of Natural Science has a new exhibit, “Archaeopteryx: Icon of Evolution” that features the best Archy ever.  Do not let that blind you, though, to the other critters on display. One of these is the best marine crocodile anywhere, a Geosaurus with an exciting evolutionary story all its own. These animals have a worldwide distribution from Brazil to Germany, but this specimen is the most complete, and shows the soft parts. Ah, the preservation of fossils in the Solnhofen limestone is amazing.

Let’s see what observations we can make from the skeleton and what conclusions we can draw. Look at this picture and get an overall impression of the fossil. The label says it is a croc, but is it? It does not look like any croc I have ever seen.

Complete Geosaurus skeleton, with skin impressions, from the Solnhofen limestone.
Geosaurus skull showing croc dentition

Head: The front end certainly looks like a modern crocodile head. The teeth are conical and striated, with the typical croc dentition:  teeth are located inside and outside the jaw line, and there are large teeth half way down the jaw.  Modern crocs use them for breaking turtle shells (see the YouTube video referenced below).

Tail: Ok, so it is a croc but it does have a very strange tail. Let’s look more closely at the tail to see if there is any support for the decision the preparator made to indicate a tail like a shark’s.

The faint skin impressions support
interpretation as a shark-like tail.

The discolored rock strongly suggests that the tail does have a shark outline, unlike that of all known modern crocodilians. Even better, compare the caudal processes (bumps on the top of the vertebra) in the area of the fin to those farther up the spine.  The processes in the tail fin area are longer and reverse orientation: they point toward the head, possibly as support for the fin. The fin is real!

Armor: This croc does not have any! There are no osteoderms (bony plates inside the skin) anywhere. The osteoderms in modern crocs do not provide complete coverage and thus are not much use as armor; however, a modern croc has muscles between its osteoderms that can stiffen up the skin during rapid land movements.  Apparently Geosaurus got along without them.

Legs: The arms are very short in proportion to the legs, quite unlike modern crocs.

Salt Gland: Many animals have glands to secrete sodium chloride because they live in or on life from the ocean and eat way to much salt. This animal is said to have chambers in the skull for a salt gland, but I cannot see it. I guess I will take their word* for it. A modern croc has a salt gland in its tongue while many birds have theirs in the skull.

Analysis: Modern crocs are slow swimmers and, thus, ambush predators. A shark-like tail suggests this was a higher speed predator. A modern croc has about 5% of its weight in osteoderms and their absence would improve the water speed at the expense of land speed. I think we have caught this croc species in the transition stage of becoming a true marine predator. It still had clawed limbs to crawl out on the land (to mate and lay eggs) but their smaller size would certainly help reduce drag. If this evolutionary path had continued, the croc’s descendants might have ended up looking like Ichthyosaurs, air-breathing reptiles that gave live birth and looked remarkably like modern dolphins. Remember, a saltwater croc in Australia is called a marine crocodile, but it does not have many adaptations to live in the marine environment besides a salt gland in its tongue.

An Ichthyosaur is a reptile completely adapted to a marine environment.
What happens when a Steneosaurus trys to
ambush an Allosaurus at the water hole

There are other crocs found in the Solnhofen limestone, including long-legged land crocs, dwarf ones, and a substantially armored one, Steneosaurus, featured by Dr. Bakker in this wonderful drawing.

To read more about the Geosaurus, check out Dr. Bakker’s blog.

References:

Wikipedia:  Criosaurus , Dakosaurus, Geosaurus
A nice discussion of aquatic crocs is at  http://en.wikipedia.org/wiki/Cricosaurus

Modern croc using those teeth on a turtle: “ahmedsadat” posting on YouTube, 2008, “Crocodile eats turtle”,  http://www.youtube.com/watch?v=cSKAXOFvi6c

*Salt glands – it is claimed that the skulls have a chamber for salt glands see Fernández and Gasparini, 2008, Naturwissenschaften. 2008, 95(1):79-84. Epub 2007 Aug 22. http://www.ncbi.nlm.nih.gov/pubmed/17712540

Dwarf crocs from the Solnhofen limestone, page 36 in Wellnhofer, 2009, Archaeopteryx, Icon of Evolution, Verlag Dr. Friedrick Pfeil.

All pictures by Neal Immega except the Dino/Croc fight which is by Dr. Bakker.

Summer Nights: Tell me more, tell me more

desert
Not Houston, but feels like it.
Creative Commons License photo credit: steve phillips

As I sit out on my balcony and watch the sun set in the evening, a thought comes to mind that is shared by millions of Houstonians. That thought is, “Boy, its hot in Houston.” Not very original or very deep, but not all the firing of my gray matter can bear the golden fruit. The next thought that is spawned is, “I like air-conditioning,” after a few musings of how my ancestors brought about all of civilization without air-conditioning. After that I start wondering how much money I have spent on the wonderful invention of the modern world. Immediately after that I think of how to cut down on my energy costs.

Here are some basics of how to do just that.

First is to learn how to read an energy bill. This is very simple and I like to start with the simple things. Some people will just pay the bill and trust that the electrical company is charging them the right amount. In the days of e-billing, it’s just that much easier to remain ignorant about how much energy you use.

The hard part about writing this is that every energy company has a slightly different bill. Not all of them have all the same bells and whistles.

Here is an example.

The most important things we are looking for on the bill are kilowatt hours used, price per kilowatt hour, and total cost. If your bill has any month by month graphic on how much electricity you use, or a yearly average, that could be useful as well.

fourmeters
Creative Commons License photo credit: this lucid moment

Once we get the number of kilowatt hours and the price per hour, we can move on to reading the electric meter. As a small child I was fascinated by the mechanical cipher and spent some time one summer afternoon deciphering its markings. 2 decades ago and in a much smaller town, my electric meter looked like a series of small clocks that go up to 10 over a rotating rotor disc. The display dials would turn to show the number of kilowatt hours used.

If you have a digital electric meter there is no challenge in reading it. It shows the current total amount of kilowatt hours that the electric meter has counted. This is not the number you have used in a week, or a month, or a year, but the total amount it has counted in its life time.

To figure out how many kilowatt hours you have used in a day, month, or year all you need is two sets of numbers. To see how many kilowatt hours you use a month, record the reading on the electrical meter at the beginning of the month and at the end of the month. Then subtract the smaller number from the larger. That will tell you how many kilowatt hours you have used in a month.

There are a number of devices and computer programs that can help chart your energy usage, such as Google PowerMeter.

Now that we know how many kilowatt hours you use, we can measure different devices to put together a picture of where the kilowatts go.

There are any number of estimators and calculators available for free on the internet (like here, here, and here). However these are all estimators. If you want to know exactly how much power any given appliance uses, you will need to use a simple watt-hour meter (kill-o-watt meter is a very simple and inexpensive one).

Once you start measuring what wattage your appliances use, you can paint a picture of your energy usage. And with that you have the knowledge to make decisions about your energy usage.

If you want to lower your energy bill, you can make simple changes, like turning off lights when you leave the room and not leaving appliances plugged in when they are not in use.

Stay tuned for the next Energy Conservation Installment.

Your Archaeopteryx Questions: Answered! [Pete Larson]

Pete Larson’s new research into the Thermopolis Archaeopteryx specimen currently on display here at the Museum is fascinating (who knew feathers could fossilize?) and we recently hosted an online discussion with Pete to showcase the new findings and give people a chance to get all their burning Archaeopteryx questions answered.

We were so happy to hear the response, the great interaction and the insightful questions asked during the event. Unfortunately, we couldn’t get to them all, so Pete graciously agreed to respond to all unanswered questions in a post here on our blog.The following questions were submitted either during the event itself, or from people who couldn’t attend, in the comments section of the post announcing the event.

And so, without further adieu…your Archaeopteryx questions, and Pete’s answers:

What is your view on the origin of avian flight?

There are two basic hypotheses for the origin of flight: A.) From the ground up – a running start from a fleet footed meat eating dinosaur. B.) From the trees down – theropods climbed into trees and at first glided from tree to tree, to escape predators or to find food. I think that the later idea is most credible. The claws on the hands of early birds, like Archaeopteryx, could have been used, in conjunction with the claws on the feet, to climb into the trees (like juvenile Watsons [sp.?] do today). This also would have limited the stress on the flight feathers and the necessity for a keeled sternum (something that Archaeopteryx does not have).

The Archaeopteryx is angry.
You wouldn’t like him when he’s angry.

What would cause such rapid burial underwater?

A change in temperature could have precipitated the crystallization of tiny calcite crystals that rained down on the organisms. The warmer the water, the more it can hold in solution. Perhaps even daily fluctuations from night to day caused this accumulation over the centuries.

With the great preservation of bones and some soft parts, what was the level of anoxia in the water column?

Because of the reef that protected this “lagoon”, the wave action was limited within the lagoon itself. If you were to measure the amount of dissolved oxygen, you would see a decrease with depth, depleted, at least in part, by resident organisms. Presumably, the bottom was very anoxic, to the point that it could not support animal life. This, however, created a great environment for fossil preservation.

What does the Archeopteryx fossil do for the “evolution of evolution,” . i.e. the progression from Darwin’s theories of natural selection and evolution to modern evolutionary theory to future understanding, both paleo and contemporary?

Soon after its discovery, arguments were made dismissing this discovery as the missing link between birds and dinosaurs. “Dinosaurs do not have feathers (let alone flight feathers), dinosaurs do not have furculae (wishbones), Archaeopteryx does not have serrated teeth (dinosaurs do), etc.”  It turns out that some, if not all, theropods (meat eating dinosaurs) have feathers, including flight feathers. Theropods have furculae (even T. rex). And some theropods have non-serrated teeth, etc.. Archaeopteryx IS the link between dinosaurs and their evolutionary offspring, birds.

In regards to the shark fossil, Hybodus what would be a modern ancestor?

Hybodus is part of the Order Hybodontiformes, of the Superorder Selachimorpha (Sharks). The entire group became extinct at the end of the age of dinosaurs – the KT boundary, 65MYBP.

When you first find these fossils are they of a different color and then change once they hit our oxygen air another wards does our oxygen change these fossil in anyway shape or form?

As one who has collected a lot of fossils from a lot of different localities and ages I can tell you that you often witness color changes. Usually this is due to the drying out of the surface of the fossil (You can test this by licking an unconserved fossil – or even a rock – and see an immediate “brightening” of the colors.) Occasionally a thin white film of gypsum (if there is pyrite in or near the specimen) can grow quickly over the surface of a fossil, literally overnight, that will hide its true color. Atmospheric oxygen is not a big problem, however some fossils, particularly those preserved with unstable minerals near or within can combine with atmospheric water and create such chemicals a sulfuric acid, that can destroy the fossil.

Can you briefly summaries the other fossil evidence for early bird-like creatures other than Archaeopteryx?

We actually have a very good record of fossil birds from a second locality (Liaoning, China where we also find feathered non-avian theropods) that is about 20 million years after Archaeopteryx (Archaeopteryx is 145 MYBP and Liaoning is 122 MYBP) in the Early Cretaceous. [For those of you who wonder what MYBP stands for it is "Millions of Years Before Present", not "Millions of Years before Pete."] Here we see a wide variety of forms, some with more advanced characters and some with very primitive characters, ie. The clawed manus (hand) and toothed skulls persists in some species but have already been lost in others. For the Jurassic, however, diversity was small and all we see are these things we call Archaeopteryx lithographica (but are probably at least two species that some would argue were at least two genera).

Can you see muscle scars on the Archaeopteryx that indicate the presence of muscles which might be used in flight, or are they too small?

Points for insertion of tendons (the tissue that bonds muscles to bones) can be seen on the bones of Archaeopteryx. They do not exactly duplicate what we see in modern birds, But then an animal that lacks a keeled sternum would be built differently then their descendents.

Did you participate? Leave us a comment here to let us know what you thought – and what we can do better next time.

Sad you missed the event? Click here to watch a recording.

Fascinated? Us too. See the exhibit.

VIDEO: Tour the Archaeopteryx exhibit with Pete Larson

VIDEO: Focus on: The Thermopolis ArchaeopteryxF