Yellowstone: Day 4
Artist Paint Pots, Mammoth Hot Springs and Life, and Midway Geyser Basin

	Our first stop was at the Artist Paint Pots area, on the way to Mammoth Hot Springs. Upper left Paint pots and mud pots are hot springs without an effluent discharge. The hot, acidic water bubbles up from below and dissolved the surrounding rock, but doesn't readily drain out of the area; the result is a muddy, bubbling "spring." Below left A fumarole is a crack or fissure where only hot steam is escaping. This one gave off a distinct hissing sound. Right Our first sight of an erupting geyser, where superheated water and steam escape forcefully from a narrow crack in the ground.

Dave DeMarais (NASA/Ames) joined us on Saturday to guide us around the Mammoth Hot Springs area. Dave works on microbiology and origins of life stuff.

Minerva Terrace is the currently active terrace at the Lower Mammoth area. The white areas are old travertine deposits, and the orange part is where water currently flows. The flowing hot water creates an environment where orange, filamentous bacteria live.

We had lunch at Upper Mammoth, a non-active terrace. Here, we met up with a film crew from the Discovery show, New Explorers.

This is a very old terrace, where weathering has cut away one side to show the cross-section. The upside-down U-shaped layering occurs as the outer layers come off and expose the inner, older layers (much like an onion). The total height of this terrace is about 10 meters!

Here's the texture in hand sample (left), and extremely close up (right). Here, the bacteria served only as nucleation sites for the calcium carbonate. Contrast this mode to today's oceans, where microorganisms secrete calcium carbonate directly.

Filamentous bacteria in pool

We took a short walk over a hill and found a small pool of water, with a well-developed bacterial mat community growing in it. Below closeups of the mat surface. The top layers are photosynthetic, and the oxygen they give off bubbles up through the water.

Left Narrow Gauge Spring, a hot spring whose effluent runs down a narrow line. Right A similar setup as Narrow Gauge, we were able to walk right into the center of this inactive spring and see the inner sides like a road cut.

Further along the back trail, we came across tree casts. Left A tree cast starts when a spring deposits material around a log or a tree. Here, a log is being covered by layers of travertine. Right The tree's organic material eventually rots away, and creates a hole in the mineral deposit.

Atop an active terrace at Upper Mammoth, we checked out steaming pools close-up.

On the way back from Mammoth, we stopped at Midway Geyser Basin, home to the Grand Prismatic Spring. Grand Prismatic is known for its jewel-bright rings of colors around the pool. The colors are caused by different bright bacterial inhabiting temperature zones from the hot interior to the cool edges. Above center Barb checks out the pH of the algal mat and above right Jay inspects the mat himself.

	Here at Grand Prismatic Spring, Chris gave his talk about various aspects of the origin of life, including, left, the helical structure of DNA. As the sun began to set and the air turned colder, steam rose up over the spring and the sun's rays shone through it--thus turning Chris' talk, right, into a spiritual-looking experience.

Sunset over Grand Prismatic Spring.