(1) Discover Life Nearby:  This is the search for life in our solar system.

(2) Sniff It Out: Do the sort of spectral analysis that might detect atmospheric gases caused by biology.

(3) Eavesdrop On ET: Otherwise known as SETI, is the effort to detect radio signals or laser flashes from technically savvy extraterrestrials.

Neat, Shostak has set the frame work for further dscussions. Note that the (1) is the search for the existance of life based molecules. That (2) is the search for life forms, whether past or present. And (3) is the search for extraterrestrial intelligence.

He says that a priori all are equally likely to be successful. Lets think again.

With respect to (1) Discover Life Nearby, lets look at the record. Using the Mars Exploration Rovers, Spirit & Opportunity, as examples, Spirit which was 2.3m wide, covered 8.81 km over 581 sols (a Martian day that is approximately an Earth day), that is approximately 19 m² per day. Given that the surface of Mars is 144,798,500 km² it will take Spirit about 7.6 × 10¹² days or 208,340,844 centuries, to examine the total surface of Mars. That is, assuming randomness, and that life did exist on Mars in the past, the quick & dirty probability of finding life on Mars on any day with current technology is 1.3 × 10^-13. We have a better idea of Mars. It is mostly barren. However, not a clue about the Europa the moon of Jupiter, that is believed to have oceans beneath its ice.

With current projections it likely that NASA will have a satellite at Europa in the 2020–2030 time frame.

So, we can make 2 types of guesses. Assuming that life started on Europa some millions ago, then the probability (from a detection perspective) of finding life on Europa is good, close to 1. However, if Europa is a liquid version of Mars, then the probability is on the order of 1 × 10^-13.

Therefore, the time frame for discovery of extraterrestrial life by (1) Discover Life Nearby, is about 2025 assuming no budgets cuts or other re-prioritizations.

With respect to (2) Sniff It Out, scientists estimate that there are about 1 x 10¹⁰ Earth like planets in our Milky Way. Lets assume that the Goldilocks Zone is a necessity. Using Pluto as the outer extreme of planets in a Star Local system, and Mars and Venus as boundaries of our Goldilocks Zone, then the approximate probability of finding one of these Earth-like planets in the Goldilocks Zone is 2.89 × 10^-2. This reduces the number of Earth-like planets capable of supporting life to 289,340,102. Or the probability of finding life on at least one of these planets (assuming life is present) is at least 3.45 × 10^-9.

I would estimate that the time frame for detecting extraterrestrial life is between today, and 35 years from now to 2047.

It could be any day now as the Dutch using the Very Large Telescope in the Chilean Andes have detected carbon monoxide on a planet hugging the star Tau Bootis that is 51 light-years away. The other end of my estimate is 2047. This is because developing a technology like the James Webb telescope was 30 years in the making.

So (2) Sniff It Out, has a better chance of finding evidence of life than (1) Discover Life Nearby.

Now how about (3) Eavesdrop On ET? As the author of the 12-year study An Introduction to Gravity Modification, it is slim. Sorry, Tarter, Shostak and all of you at the SETI Institute. But wait, I haven’t finished.

Look at our civilization. In 1895 Guglielmo Marconi proved that long distance radio transmission was possible. In 117 years we have exponentially evolved our technological sophistication to what it is today, 2012.

As the author of the 12-year study An Introduction to Gravity Modification I have proposed (see page 195) the existence of subspace, where everything is probabilistic, and light speed is not a restriction. Therefore, if confirmed, there is the strong possibility that by 2025/2035 this planet will go radio silent, because all our transmissions will be through subspace.

That is, the window to observe a radio intelligent extraterrestrial civilization is about 100 to 150 years, then they go silent. 100–150 years is an immensely thin slice or duration compared to the distances of stars even within our own galaxy, the Milky Way. Or the probability of detecting extraterrestrial radio transmissions within our own galaxy is approximately 1.25 × 10^-6. It is actually a little better than this but I am using quick & dirty for this blog posting, and this will do.  This is much better than a posteriori 1 × 10^-13 for (1) Discover Life Nearby and  3.45 x 10^-9 for (2) Sniff It Out.

So SETI, keep eavesdropping, and we can expect confirmation of Extraterrestrial Life by 2047 latest.

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Benjamin T Solomon is the author & principal investigator of the 12-year study into the theoretical & technological feasibility of gravitation modification, titled An Introduction to Gravity Modification, to achieve interstellar travel in our lifetimes. For more information visit iSETI LLC, Interstellar Space Exploration Technology Initiative