Rock Eating Cacti

Did you know there are cacti that live on bare rocks? It's true! The giant cardon cactus of Baja Mexico not only lives on rocks, but drills its roots into them for anchorage!

So how on earth does a plant accomplish this feat? The answer lies in a symbiotic relationship between the giant cardon cactus (Pachycereus pringlei) and an endophytic bacterium. The bacteria produce an acid that breaks the rock down into the minerals the the cactus needs. In return, the cactus allows the bacteria to live in its roots, suppling them with water, carbon and shelter. The acid that the bacteria make also allows the cactus's roots to bore into the rock by dissolving it. This process not only benefits the cacti and bacteria, but also breaks the rock down into soil at an accelerated rate so that other vegitation can grow there.
To continue the mutual symbiosis, P. pringlei "packages" the bacteria with it seeds. The seeds are then spread via bat or bird droppings which supply the young cardon cacti with nutrients until the bacteria can establish themselves.

Sources:
http://thenewcreationism.wordpress.com/2009/09/02/rock-dissolving-bacteria-in-desert-cacti/
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8209000/8209687.stm
http://worldwidescience.org/
http://www.sciencedirect.com/science/journal/00988472

All images courtesy of BBC News

Quark Quirks

Can you imagine 3 marbles floating around the vastness of outer space? If you can, you can imagine the inside of a proton.

Protons, although tiny, are not the smallest particles around, the quark is. To give you an idea of just how small a quark is, imagine a pea orbiting a baseball 20 miles away. That is the atom. Now take that baseball, magnify to the size of the Milky Way, and drop a marble in there. The marble is the quark. Starting to get the picture? I'm just getting a headache! In fact, quarks are so small they may have no size at all! Scientist refer to them as point-like-objects.

Quarks come in 3 different varieties: up, down, charm, strange, top and bottom. Up and down quarks are the ones that make up protons and neutrons. The up quark has a positive charge of 2/3, and the down quark has a negative charge of 1/3. Quarks are never found alone, they always come sets. The most common sets are baryons, which are three quark combinations that include protons and neutrons. The neutron has 1 up quark and 2 down quarks giving it an overall charge of 0. A proton, on the other hand, has 2 up quarks and 1 down quark giving a positive change of 1.

The other four types of quarks are much more massive than up and down quarks, and therefore less stable. The top quark is the most massive of all quarks. It has a mass roughly equivalent to a gold atom, and can remain in existence for more than a billionth of a second!

Here's an fun thing to leave you pondering: according to leading theories, the three quarks in a proton are not alone, but surrounded by "virtual quarks" that blink in and out of existence!

Sources:

hyperphysics.phy-astr.gsu.edu/HBASE/Particles/

www.sudan.umn.edu/

World Book Encyclopedia, 1997 Edition

World Book Encyclopedia, 2008 Edition

Mass Concentrations

Back in 1967 NASA was shocked when they observed a new lunar satellite orbiting the moon in an irregular pattern. The satellite would be orbiting normally, and then dip toward the moon's surface without warning, gain speed, and shoot back up into normal orbit. Investigation of this problem led to the discovery of mass concentrations.
Mass concentrations or "mascons" are just that, concentrations of mass. The word can be used in different ways, but the most common refers to a large pocket of high density matter on or under the surface of a terrestrial body. In the moon's case, mascons are 6km thick sheets of basalt which form the maria.

Now that I have explained a little of what mascons are, I can tell you what they do. Because mascons have more mass than the surrounding crust, they have a greater gravitational pull. This is why things orbiting the moon dip and sway as they pass over a mare; the mare's mascon is pulling the satellite out of orbit. Because of this, spacecraft cannot safely orbit the moon for more than 2 months*. (Luckily NASA discovered this before they sent people to the moon.)
Believe it or not, the Earth has mascons too! They are not as extreme as the moon's, but still do change the weight of objects over them. Two of the largest and strongest are Hawaii and a large crater in Antarctica.

*There are four stable orbits around the moon that do not pass over mascons, and safe orbits can be achieved over mascons with the aid of computers and rockets.
Sources:
http://science.nasa.gov/headlines/y2006/06nov_loworbit.htm
http://earthobservatory.nasa.gov/IOTD/view.php?id=6862
Word Book Encyclopedia 1997 Edition
http://www.higp.hawaii.edu/

Top two photos courtesy of NASA
Lower photo from Google Earth