Wednesday 6 April 2011

&^%$%^& EXAM 3 === Friday 22 April 2011 &^%^^&

Sara says: Thursday 7 April 7PM A1514 will meet at 7:30PM instead of 7PM

************* Mars : Myths and Realities ****************

Visual appearance of Mars Even at its closest to us (about 35 million miles) Mars looks to your naked eye only like a bright red star. (It looks red because there is lots of iron oxide - rusty sand- on the planet). Back in 2003, there arose an "internet myth" that Mars in August 2003 would look as big as the full moon does. Mars came particularly close to the Earth in 2003. This "Mars as big as full Moon" was utter nonsense, and astronomers tried to set people straight, but the myth persists. I still get emails and phone calls asking when Mars is going to "look like the full moon" again.

Lesson to be learned: Don't believe everything you see on the internet! (But you knew that, right?)(By the way, I have $20million US that I need your help transfering into the US. Just send your social security and bank account number to my Nigerian email account.....)

Schiaparelli drawing of Mars The late 19th c. Italian astronomer made drawing like this of Mars. Some of the features are real, most (particularly the linear "canali") are not.

Percival Lowells canals on Mars Around 1900, Percival Lowell ("self funded" astronomer from an old money Boston family) popularized the idea that there was a Martian civilization that built "canals" to bring water from polar caps to crops. What was Lowell seeing?? He convinced many that the "canals" were really there.

Soap ad around 1900 In the early 20th c. , everyone "knew" there was a Martian civilization, mainly due to writings of Lowell. It was all nonsense, of course.

Earth and Mars to scale Mars has a diameter about 0.53 that of Earth.

Mars from Earth Taken at the famous Lowell Observatory, in Flagstaff. Lowell was founded (and funded) by Percival Lowell. Lowell Observatory is one of the largest observatories not associated with a university or government, and part of its budget still comes from an endowment fund left by PL. So, even though PL was way wrong about Mars, he left an enduring positive legacy for astronomy.

Using Earth-based telescopes, we can see only some vague dark and light patches on Mars, along with polar ice caps. These dark patches sometimes appear to change from week to week. This was another observation that Lowell used as evidence for life on Mars. He said the changing markings were due to crops growing. We now know that the changing patterns are due to wind blown dust covering and uncovering underlying areas on the planet.

The polar ice caps are composed of water ice and frozen CO2 (dry ice). The CO2 cycles between north and south polar caps with the seasons. Mars has some striking similarities to Earth. It rotates in 24.6 hours (called a "sol"). The poles are tilted about the same as the Earth's, so there are seasons somewhat like those on Earth.

First spacecraft images of Mars Some people held onto myths about Mars until the first spacecraft flybys of Mars in the 1960s showed no canals.

Impact craters on Mars Huge old (inactive) volcanoes on Mars Mars today appears to be a geologically dead world. However, it was probably once an active world, with huge volcanoes that dwarf any on Earth.

*** Spacecraft exploration of Mars****

Around 50 different spacecraft have been launched to explore Mars, by the US, Russia, and the Europeans. Probably more have failed than have worked.

Sagan and Viking Carl Sagan next to Viking mockup in Death Valley. The two mid-1970s Viking landers (and also 2 orbiters) comprised a very ambitious and expensive set of missions to explore Mars and look for signs of life. Although the robotic chemistry lab that analyzed Martian soil (see picture of soil excavation trench below) found some unexpected chemical reactions, only a very few scientists think Viking found evidence for life. (As Carl was fond of saying "Extraordinary claims require extraordinary evidence") In 2008, the lander Phoenix found tentative evidence for perchlorates in the Martian soil, a result which may help explain what Viking found.

After Viking failed to find definitive proof of life on Mars, interest in (and funding for) Mars missions waned for several decades.

About 10 years ago, new interest in Mars lead to new modern missions to Mars, particularly a series of robots rovers that have scooted around the Martian surface.

Viking on Mars 1976 You can see some trenches dug by the robotic arm in its search for life on Mars.

Viking on Mars 1976

Mars rovers Sojourner was a small test rover that landed on Mars in the late 1990s. Spirit and Opportunity are the 2 MERs (Mars Exploration Rovers) that landed on Mars around 2004- both are still working and sending back data! Phoenix Mars Lander landed on Mars in 2008. The largest rover , MSL (Mars Science Laboratory) will (we hope) be on Mars in 2011-13 time frame.

Mars rover mockups

THE ultimate dream of Mars exploration is evidence for life. One of the lesser goals of Mars exploration is to find water. I think most everyone now agrees that we have pretty solid proof that there are large deposits of water ice on Mars. This comes from a number of different pieces of evidence gathered by spacecraft in the first decade of the 21st century.

Definitive proof of liquid water on Mars What can I say- an image that appeared on the internet 1 April 2005.

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One argument for existence of water ice on Mars in high latitude areas is the existence of patterned ground which looks strikingly like permafrost (subsoil ice) regions on Earth. These features, which suggest polygons, are found in permafrost on Earth. The next 2 pictures are of patterned ground- the first on Mars, the second on Devon Island, in northern Canada:

Patterned ground from Phoenix Phoenix as in 2008 lander on Mars not Phoenix, AZ. (Ain't no permafrost in Phoenix AZ).

Patterned ground Devon Island Devon Island is in the north of Canada (on Earth).

Sublimating ice on Mars Phoenix dug a trench uncovering some white stuff. In a few days, it was gone, presumably sublimated away. From temperature and pressure, this stuff behaves exactly as water ice would have.

Ice in crater This is a photo from Mars Express of a crater whose bottom is shielded from direct sunlight. Mars Express is a spacecraft which has been orbiting Mars since 2004. It was sent by the European Space Agency. It had a lander (the Beagle 2), but that failed. The orbiter has worked well, and is scheduled to work until at least 2012.

Dry river bed? Martian flow features Ancient flow features on Mars. What was flowing and when?

Many scientists think that Mars was "warm and wet" several billion years ago. If the atmosphere was much thicker than it is now, the greenhouse effect could have made Mars warm enough for liquid water to exist. At present, the atmosphere is so thin that there is very little greenhouse warming.

Phoenix spacecraft descending to surface of Mars, snapped by MRO (Mars Reconnaissance Orbiter) One Terran spacecraft taking a picture another Terran spacecraft around Mars! What amazing times we live in!!

Over the past 6 or 7 years, there have been at least 2 working spacecraft orbiting Mars or roving about on its surface at all times.

MRO images Opportunity Another instance of one robotic tourist snapping a photo of another robotic tourist. Photo of rover Opportunity from orbiting Mars Reconnaissance Orbiter.

Opportunity MER (Mars Excursion Rover) Opportunity found and imaged its own heat shield (or is that a fender from a Martian '37 Chevy?)

Mars and Earth Left side is Morocco, right side is Mars.

Martian sunset A dusty sunset on Mars.

Martian atmosphere and weather The Martian atmosphere is similar in chemical composition to that of Venus (mostly CO2), but the surface pressure of the atmosphere on Mars is 0.00006 that of Venus and 0.005 that of Earth. Why is the Martian atmosphere so thin? Probably a combination of several things: (1) Mars has only a weak magnetic field, and so the Sun's solar wind has been blasting the atmosphere directly for billions of years (2) The surface gravity of Mars is about 40% that of Earth, so it is much easier for atmospheric gas molecules to simply fly into space from Mars than from Earth. (3) Mars appears to have been pretty "dead" geologically for quite a while. No recent active volcanoes have pumped subsurface gases trapped beneath the surface into the atmosphere.

Because of the thin atmosphere, there is a larger day/night temperature swing compared to that on Earth, even though Mars has a "day" (called a sol) that is only a little longer than our day (one sol = 24.6 hours). At the Martian equator in summer at noon, the temperature might rise to almost the temperature in this classroom, but at night it would drop to temperatures more characteristic of the polar regions on Earth. The overall average surface temperature is about 210K (about -81 F - thats negative 81 F).

We know little of the history of the atmosphere of Mars. If the "flow features" we see were caused by liquid water, the surface temperature and pressure must have been significantly higher in the distant past than it is today. Maybe Mars once had a much thicker CO2 atmosphere that produced greenhouse warming??

Any future Martians here?? Is the first human who will walk on Mars alive today, or is she still generations in the future?

Carl Sagan argued passionately for an eventually self-sustaining human colony on Mars, so that the human race would survive if the Earth is ruined, either by our own folly (e.g. all out nuclear war) or by a natural disaster of planet-wide destructive power (e.g. a 200 mile diameter asteroid strike).

We could do it! There is water on Mars and energy from the Sun. Water + energy + human brain power= possibility of a true New World. WILL WE?