Today: Life in Space
Life on Mars? •
For centuries, people have speculated about the possibility of life on Mars because of Mars’ proximity and similarity to Earth
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In late 19 century, people once believed that there are canals on Mars (implying old civilizations) --- turned out to be optical illusions
Mars canals, as seen by astronomer Percival Lowell, 1898
Life on Mars? •
In early 20 century, astronomers found neither water nor oxygen were present in Mars atmosphere
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Mariner 4: the first successful flyby of Mars, shows no signs of life Craters on Mars, as seen by Mariner 4 in 1965
Life on Mars - more recent explorations •
NASA’s Mars Exploration Rover Mission involving two rovers, Spirit and Opportunity (2003-2011)
Picture taken by Spirit rover
Life on Mars - more recent explorations •
Opportunity rover sent back much evidence that a wide area on Mars was soaked in liquid water (presence of hematite concretions)
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Spirit rover detected goethite, which forms only in the presence of water spherical hematite (~100-250 micron)
Life on Mars - this Sunday!! •
Curiosity, the latest rover of NASA’s Mars Exploration Program, will land on Mars this Sunday!!
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It carries state-of-the-art instruments that can analyze soils and rocks on Mars --- seeking for the signs of past habitability
Life on Mars - this Sunday!! Curiosity Mars Rover landing life viewing!! August 5, 6pm, IfA Auditorium
Astronomers from the IfA, and planetologists from the Hawaii Institute of Geophysics & Planetology, and the UH Dept. of Geology will talk about the mission and its importance, and to answer your questions.
Life outside our solar system?
How many intelligent civilizations? The Drake Equation
Number of technological, intelligent civilizations in the Milky Way galaxy
=
Rate of star formation, averaged over the galaxy
X
Fraction of stars having planetary systems
Fraction of those Fraction of those which evolve X with life intelligent life
X
× X
Average number of habitable planets per system
Fraction of those which develop X technological society
×
X
Average lifetime of a technologically competent civilization
Your mission: Determining how many civilizations are out there? • Form 6 groups (2 people per group) • You are highly trained scientists, using your vast knowledge of astronomy to determine the answer to the Drake Equation • You will need to talk to other groups to find out the probabilities for the factors that make up the Drake Equation • In your groups, you discuss the different factors that make up the Drake Equation, and make (educated, if possible) guesses at the values • Present your results in the end of class, I will give a brief summary
Explanations of Factors in The Drake Equation 1. Rate of Star Formation: this is just a measurement of the number of stars available in the galaxy to host planets. A reasonable number is 5-10 / yr
2. Fraction of Stars with Planets: we have just begun to pin down this number with observations of extrasolar planets. A good number is between 0.1 and 0.5, but could be higher if there are many unobservable planets…
Explanations of Factors in The Drake Equation cont. 3. Average Number of Habitable Planets: Of
the systems with planets, what is the number of habitable planets per system? We appear to have only one (Earth), but maybe more are waiting to be discovered?
3. Fraction of Habitable Planets that Have Life: Does life form automatically when it has the chance? Then this number would be 1. But if it’s still a complete fluke that life is formed even if the conditions are right, then this number would be small, like 0.01
Explanations of Factors in The Drake Equation cont. 5. If Life Forms, What is the Chance that Intelligence Evolves?: This is a question of
whether or not intelligence is a natural stage in evolution. If it evolves every time, this number would be 1, and would be smaller if intelligence is a rare event.
6. Fraction of Intelligent Species that Develop Complex Technology: Do intelligent species always strive for technology (specifically, communications technology) or is this rare? If it’s common, choose something near 1. If it’s rare, choose something very small
Explanations of Factors in The Drake Equation cont. 7. Lifetime of a Civilization Capable of Communicating with Us: This is just the
average time that a technological civilization exists. Ancient Rome lasted for thousands of years, than crumbled. Will we destroy ourselves? Reasonable numbers would be anywhere from 2000 years to 10,000 years
7. Anything else that needs to be taken into account?
Explanations of Factors in The Drake Equation cont. Once you have an idea what the factors are,
Multiply Them Up!
Is this the kind of number you expected? Do you believe we could contact other intelligent beings?
Drake Equation Estimate Number of “technical civilizations” currently in Milky Way:
N = (SFR) x nhabit planets x f life x f intel x f tech x L (Lifetime) = 10 x 1 x 0.001 x 0.1 x 1 x L = 0.001 L Some pure guesses, but it all comes down to L: we can only project our own natures onto the aliens
Drake Equation Estimates Drake Equation for the number of “technical civilizations” currently in Milky Way: N = (SFR) x nhabit planets x f life x f intel x f tech x L Lifetime could be huge (Giga years) for successes, or is the power of technology so de-stabilizing that civilizations cannot survive it for more than 1000 years = L??
Pessimistic Estimate Drake Equation for the number of “technical civilizations” currently in Milky Way: N = 0.001 x L = 0.001 x 1000 years = 1 Technical Civilization in our Galaxy Pessimistic: this is Us! Probably alone until we destroy ourselves within several centuries
Optimistic Estimate Drake Equation for the number of “technical civilizations” currently in Milky Way:
N = 0.001 x L = 0.001 x 1 Billion years = 1 Million Technical Civilizations Optimistic: a Swarming “Galactic Club”, should not be too hard to find this “super-civilization”
The Drake Equation • In reality, almost all the terms have no conclusive answer yet, so anybody’s guess is as good as anyone else!
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