Astrobiology and SETI:

The Search for Extraterrestrial Intelligence

Victor-Andrei Bodiut, S2574608

Coordinator: prof. dr. Peter Barthel

Course: Astrobiology – Minor Astronomy through Space and Time

University of Groningen

17-04-2016

Figure 2 – Center of the Milky Way

Figure 1 – Very Large Array, New Mexico – “Listening the Skies”

As suggested by its name, astrobiology is the biology

of the universe. It studies life outside Earth, how it got there,

what it looks like and how it will evolve. For these reasons,

astrobiology is a very big interdisciplinary field, with scientists

from physics, biology, geology, astronomy, chemistry,

ecology, sociology and more, all working together to find an

answer to arguably the biggest question ever asked by

humanity: are we alone? The SETI Institute (Search for

Extraterrestrial Intelligence) has been tackling this issue for

some decades now. A great team of ~ 150 scientists, together with engineers, computer

programmers and technical staff is divided in three centers: the center for SETI research, the

Carl Sagan center for studying life on and off Earth and the Education and Public Outreach

(EPO) center.

Tasks of the EPO center include educating the larger public and passionate people

onto the topic of extraterrestrial life, teaching in academia or developing SETI in the social

media.

The Carl Sagan center involves the majority of the institute’s members. Their focus

involves speculating about how life should look like in different mediums (bio-signatures),

how life generates and spreads and the necessary conditions for life (i.e. if life could survive in

worlds without sunlight, without water or in sub-zero temperatures).

Within the solar system, there are a few “hot-spots” that show

very promising for microbial life (perhaps even complex life).

For instance, scientists are trying to figure out if Mars contains

microbial life under the soil. Figure 3 shows a self-portrait of

NASA's Curiosity Mars rover at "Namib Dune", where the

rover's activities included scuffing into the dune with a wheel

and scooping samples of sand for laboratory analysis.

It is almost a consensus in the astrobiology community that

some sort of liquid is a necessary prerequisite for life to

evolve. Water is by far the most prominent candidate. Recent

discoveries show that water is quite abundant in the

observable universe, existing at present on 3 distinct objects in

our solar system alone – Earth, Europa and Enceladus and

used to exist on another 2 – Mars and Venus.

Figure 3 - Self-portrait of NASA's Curiosity rover

Figure 2 – SETI Institute, California

Thus, the ocean of water under the frozen

surface of Europa, one of Jupiter’s moons is

of great interest (see Figure 4). The fact that

its icy surface is without craters, very young in

appearance (in fact ever-changing) points

towards a liquid ocean beneath. Its

magnetism indicates a probable iron-nickel

core and seems to confirm the existence of

water.

But, although water is extremely important in

the discussion of life elsewhere, astrobiologists are proposing other liquids as well, such as

ammonia, liquid methane and even sulfuric acid or formaldehyde. It is quite hard to believe

that such toxic substances could harbor life. However, when keeping an open-mind, one can

speculate that these types of substances are only toxic to us because we have evolved in a

watery world. Other organisms may evolve in

fundamentally different environments and,

perhaps, find water as toxic.

Enceladus, a moon of Saturn is showing cryo-

volcanoes, volcanoes that spurt volatiles such as

water, methane or ammonia, instead of molten

rock/lava (see Figure 5). There are chances that

these spurts could contain organic structures.

Moreover, it is believed that some form of life

could exist in the liquid hydrocarbon lakes on

Saturn’s moon, Titan. We know for a fact that Titan is very

similar to Earth in the sense that it has at atmosphere, clouds,

it rains, and lakes and seas form. The key difference is that the

liquid on Titan is not water, but liquid ethane, methane,

propane or dissolved nitrogen. Figure 6 depicts “Cassini’s

synthetic mosaic of Titan's North Polar Region, showing

hydrocarbon seas, lakes and tributary networks. Blue coloring

indicates low radar reflectivity areas, caused by bodies of liquid

ethane, methane and dissolved nitrogen”. In addition, liquid

water seems to be frozen in the slush beneath the crust of ice.

Figure 3 - The fascinating surface of Jupiter’s icy moon Europa

Figure 6 - Titan's North Polar Region

Figure 5 – Ice Plumes on Enceladus

Figure 4 – The Surprising Surface of Europa

From learning about extremophiles, beings

that thrive in very harsh environmental

conditions (e.g. very high or low pressure or

temperature, very salty or alkaline mediums,

no sunlight, etc.) we have updated our

understating of life in the universe. In the last

decades “the cosmos seems to be more and

more bio-friendly” (see Figure 7 for an

example).

Lastly, a handful of people in the SETI

Institute dedicate their careers fully to finding

experimental evidence of extraterrestrial

intelligence (as opposed to non-evolved life) and settle the big question once and for all. The

SETI research center is focusing on intelligent life elsewhere that has learned to use

transmission technology to emit signals of some sort. The key question to ask here is, even if

they did/are doing/will do so, how likely is it that we will be able to detect such a signal?

There are no definitive answers or guarantees when it comes to this, but we do have an idea

about what might be required for a successful detection. The so-called Drake equation (after

American astronomer and astrophysicist Frank Drake) helps us structure the way of thinking

in this pursuit. Unlike most equations however, there is no clear-cut in the Drake equation.

We can learn more and more about each of its unknown factors and in turn make our search

more efficient and accurate, but until SETI succeeds (i.e. finds intelligent life elsewhere) or is

disproved (i.e. finds that we are the only form of intelligent life in our local part of the

universe) there will not be a definitive answer. The Drake equation attempts to estimate the

number of technological civilizations in the Milky-Way galaxy that we could have contact

with. It is usually written as in Figure 8, where:

Figure 8 – The Drake Equation

Figure 7 – Thermophiles, Yellowstone National Park

N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions

are detectable. This is what SETI tries to estimate.

R* = The rate of formation of stars that can have planets in a galaxy, in terms of stars/year.

Fp = The fraction of those stars with planetary systems (e.g. like the Sun has planets orbiting

around it).

Ne = The average number of planets, per solar system, with an environment suitable for life.

Fl = The fraction of suitable planets on which life actually appears.

Fi = The fraction of life bearing planets on which intelligent life emerges.

Fc = The fraction of civilizations that develop a technology that releases detectable signs of

their existence into space.

L = The longevity factor, the average length of time such civilizations release detectable

signals into space.

Although by now we know quite a

great deal about the first 3 variables of

the equation, there is still a lot of

variance in the results. A very

important aspect is the fraction of

Earth-like rocky exoplanets that has

increased exponentially with the

success of the Kepler mission (see

Figure 9). When asked in an interview

whether extraterrestrial intelligence is

possible or probable, Jill Tarter

(American astronomer and former director of the Center for SETI Research) said that from a

scientific perspective, there is no certain answer. If with increasing technology we would have

found that it is very improbable for other stars to be orbited by planets, the chances for

intelligent life elsewhere would have been almost null. However, the evidence so far shows

the contrary. There are thousands of planetary candidates from the Kepler spacecraft

mission, and around a thousand more from ground-based search. It basically looks like the

vast majority, if not all the stars have planets.

The fractions of existing life, intelligent life or civilizations with communication technologies

are a highly debated topic with no final answer still. The number two is crucial in this

Figure 9 – Exoplanets before Kepler (left) vs after Kepler (right)

discussion. Until now, we have one example of life, us. It could be the case that the chemical

combinations and biology needed for life are unique on Earth. The moment we find another

independent origin of life, a different genesis, it will mean not just that life is a bit more

probable, but basically everywhere. “If you are going to have two examples of something,

you are going to have many more”.

In order to make progress, very crude estimates of the uncertainties have to be made

sometimes. It is believed that the rate of star formation R*, as well as the number of planets in

a solar system Ne are close to 10, while the fractions Fl, Fi are less than 1 (0<F<1), with Fc much

less than 1. By far the most uncertainty lies in the last variable L, the longevity factor. As the

other components multiplied are thought to yield approximately 1, some have thought that

the Drake equation can be reduced to a more parsimonious version: N = L. From this

perspective, it was realized that unless L is very large, N will be small. In other words, unless

civilizations exists, survive and send signals for a very long time, the number of detectable

civilizations will be very small. By reversing this line of thought, it is rationalized that if,

somewhere in the near future, SETI will detect an alien signal, this would instantly mean that L

is very large. Otherwise, the detection could not have been possible (i.e. highly unlikely) so

shortly. It is impossible to detect a signal unless two societies are close both in space (signal

detection possible) and time (co-temporality). Physicist Philip Morrison summarizes this idea

by stating that SETI is the archaeology of the future. By that he means that because the

speed of light is finite (~ 300.000 km/s), any detection of a distant civilization will be looking

at its past by the time the signals reach us. Furthermore, the fact that L must be large for a

successful detection to happen tells something about our own future. We will learn that we

can have a long future as an intelligent species and not destroy our planet and its inhabitants

in “a blink of a cosmic eye”.

SETI has encountered serious difficulties over the years. One example is dealing with

transient signals. If we detect momentary

signals, for a very brief time, it is very hard to

say if the signal comes from an alien technology

or our own. Moreover, any astrophysical signal,

such as gamma-ray bursts, pulsars, supernovae

or stellar collisions have to be separated from

technological signals (see Figure 10). In that

sense, the SETI research team is particularly

focusing on signals that are deliberately

engineered by an intelligent civilization, in both

radio and optical measurements.

Figure 10 – Color Coded Gamma-ray Bursts

In the radio observations, SETI looks for narrow-

band single-channel signals, frequency

compression. Astrophysical research would emit a

range of frequencies in search for signals that

spread out across a larger bend of radio

frequencies. Similarly, the optical research at SETI

uses time-compression, searching for very short,

bright events or pulses, like some powerful laser

flash. The assumption is that nature itself seems

unable to create such events and they can only be

signs of intelligent alien technology. Still, there is an

ongoing communication between the SETI and the astronomical community, in the sense

that SETI is very curious about the anomalies or artifacts in the data from astronomy. They

are continually asking the astronomer community to keep an eye for any unexpected results

or signals (e.g. see project SERENDIP). Maybe an alien signal lies precisely in these anomalies,

just like astrophysicist Jocelyn Bell discovered radio pulsars in what were thought to be

artifacts of noise (see Figure 11). It may very well be the case that through a serendipitous

discovery of the astronomical community, we will finally say “oh yes, of course, that’s what

they’re doing”.

Unlike the Carl Sagan Center or the

Education and Public Outreach Center which

receive grants from NASA, NSF, etc. on a constant

basis, the Center for SETI Research is nowadays

mostly privately funded.

In 1997, SETI had to think of the best ways to

structure the funding for further research. One of

the ideas was the development of a very large

array of small-sized radio telescopes, placed

across a large surface of land. The Allen Telescope

Array has been working since 2007 with 42 operational dishes, and a total of 350 being

planned, but constantly facing funding limitations (see Figure 12).

In optical telescopes, the larger the mirrors of the telescope, the better the resolution and

sensitivity. Similarly, in radio telescopes, the larger the antenna, the more sensitive the

telescope, the fainter the signals it can detect. The interesting thing is that by placing many

small antennas and pointing them in different directions, the ATA is able to cover a very large

area of the sky at once (~ 100-200 degrees2 at any given moment). This was great news for

Figure 11 – First Observation of Pulsar Pulses

Figure 12 – The Allen Telescope Array Looking for Candidate

Alien Megastructure

SETI. Another advantage of such a design is the

speed with which SETI can navigate through the

sky and explore targets throughout the galaxy,

making the ATA a very good telescope for

continue (24/7) imaging. Radio imaging can be

processed and ready for inspection in a matter

of hours. This speed is translated in the multi-

tasking nature of the telescope as well. ATA can,

for instance, look for a distant radio galaxy and

picture it, at the same time analyzing all the sun-

like stars in our Milky-Way that are on the same

patch of the sky as the distant galaxy. Another key

advantage of the ATA is that by changing the digital commands, one can use the telescope

in a completely different way. There are about 1000 sun-like stars within a range of 100 light-

years from us. SETI focuses on these star systems in particular. Since the Kepler mission

successfully identified planetary systems, the ATA has been focusing on the very same 100

degrees2 of the sky, specifically looking at the planets that seem suitable to foster life.

Researchers at SETI using the ATA can do their job sitting at home in their pajamas.

Everything is computerized, in the sense that program scripts are sent from any remote

location to the main server of the ATA, and the telescope will execute and respond. The

program is smart enough that whenever something interesting happens, such as an

uncommon, interesting signal, it gets followed up on until a point of high certainty. Only after

that scientists are informed and can manually check the signal. Moreover, the study-at-home

application for SETI came along and was received

with a tremendous interest by people. Figure 13

shows SETI screensaver from a home-user who

volunteered to donate computer power for signal

analysis. Nowadays, there are all kinds of home

projects that people can contribute to, such as

protein and cancer research, counting craters for

NASA and other great citizen science. If a signal is

received, say, from the Arecibo telescope in Puerto

Rico (see Figure 14) from a particular spot in the sky,

it does not necessarily mean much. It can be noise or

be some sort of interference. It has to be followed up

on. The interesting part comes if the signal persists in

Figure 13 – SETI Home Screensaver

Figure 14 - Arecibo Observatory, Puerto Rico -

the same patch of sky when repeatedly scanning it

across time. This is where the study-at-home

enterprise plays a crucial role, as it scans again the sky

on a yearly basis and compare the data with previous

years. So far, no replication has been found.

Except for distant stars and galaxies, SETI does

not exclude the possibility of intelligent technology

being present in our own solar system, possibly even

analyzing or sending us signals from rather close-by

(e.g. a spacecraft). The search approach for this type of

events differs from the more broad-based general SETI

search. One of the assumptions or criteria that is supposed to differentiate between an alien

technology vs our own is that we expect a point-source signal moving across the sky. If a

point-source signal would have been coming from inside our solar-system, it would have a

totally different Doppler signature and would possibly be dismissed by the computer

programs. One step forward in this regard is to accompany the spectroscopic data with radio

imaging of the event. If, based on the radio images, the signal is still interesting, it will be

followed up on. The successor of Hubble, NASA’s James Webb Space Telescope will

investigate our solar system, in addition to looking at distant stars, galaxies and

exoplanets (see Figure 15).

Project Phoenix was SETI’s most sensitive and comprehensive search. As a

follow-up on the NASA SETI program that was once again cancelled because of

financial problems, project Phoenix was sustained 100% through private funding.

Firstly, the measurements were made in New South Wales, Australia at the Parkes

Radio Telescope, then moved to National Radio Astronomy Observatory in Green

Bank, West Virginia and ended at the world’s largest radio dish antenna in Arecibo

Observatory, Puerto Rico (see again Figure 14). Here, as an attempt to

communicate with extraterrestrial intelligence, the Arecibo Message was

transmitted to the globular cluster Messier 13 (~ 25.000 light-years away). Figure

15 displays the binary message in color, although the real message was black and

white. “It consists, among other things, of the Arecibo telescope, our solar system,

DNA, a stick figure of a human, and some of the bio-chemicals of earthly life”.

In addition, SETI has used the Very Large Array in New Mexico, University of

California's Lick Observatory and the Big Ear radio observatory in Ohio as part of the Planetary

Society's Project META.

Figure 15 - NASA's James Webb Space Telescope Project

Figure 15 – The Arecibo

Message

Some constructive criticism regarding the messages that we’ve sent

in the Voyager twin satellites has been raised on several occasions.

The Voyager spacecraft is now at an approximate distance of

more than 134 AU (astronomical units), alone, quietly floating in

interstellar space. The contact with the spacecraft will be lost in 2025

or so and its first contact with another star is estimated in ~ 40.000

years. On the golden record (see Figure 17), we have painted the

human race as almost flawless or angel-like (for the full phonograph

records, see https://www.youtube.com/watch?v=DpptII291aI ).

Figure 18 shows President Jimmy Carter’s letter on the Voyager

probe.

As we all know, that is not the case. As beautiful and brilliant as humans can be, we have also

faced wars, genocides, disease, poverty, famine, mass extinction and so on. In addition, the

message did not focus a whole lot on the other forms of

life on the planet. To provide a more comprehensive

picture of ourselves, an initiative began in 2009 to

include another “cosmic message in a bottle” on the

New Horizons spacecraft after it finished the data

transfer on the close-by pass near Pluto (for further

interest, please see the sites:

http://oneearthmessage.org/ and

https://www.newhorizonsmessage.com/).

Probability analysis says that the chances of

being the only ones are very low, but thus far there is

no proof to show otherwise. This led to the so-called

Fermi paradox. Developed by Nobel Prize laureate in

Physics, Enrico Fermi and American astrophysicist

Michael H. Hart, the Fermi paradox is basically the

apparent contradiction between the high probability

estimates (e.g. following the Drake equation) for the

existence of extraterrestrial civilizations and the lack of

observational evidence so far. The paradox is built on

several foundations. Firstly, the fact that our galaxy

alone contains billions of Sun-like stars, many of which

are much older than our solar system, thus having had

much more time for developing intelligent life. Secondly, many of these stars must be orbited

Figure 17 - Cover of the Voyager Golden

Record

Figure 18 – Jimmy Carter’s Letter on Voyager

by Earth-like planets, and if we take Earth as a proper environment for intelligent life, this

could happen on any of these other planets. Thirdly, at one point in their development, some

of the alien civilizations should have develop space-travelling, as we are currently trying to.

And lastly, the Milky-Way galaxy could be traversed in ~ 1 million years even at the slow-

paced space travel that we can imagine at the moment, possibly even much faster by a more

advanced civilization. Thus, considering all of these, Fermi himself asked questions like

“Where is everybody?” meaning that some form of alien life should have paid us a visit so far.

Many solutions have been proposed, more or less probable, such as that there is no other

life, that we are the only ones to evolve intelligence, that civilizations destroy themselves

internally or externally, that aliens have actually found us, but decided to avoid contact, the

Zoo hypothesis that says that aliens are here, checking us all the time and so on. Phil

Morrison and Giuseppe Cocconi (fathers of SETI) wrote in the last sentence of the 1959 paper

in Nature on SETI: “Probability of success is a difficult estimate, but if we never search the

chance of success is zero”.

On a more general and sensitive note, I would like to end in Jill Tarter’s words:

“Humans have pondered, wanting to know where did we come from, why are we here, how

did we arrive, how do we fit in, where are we going. I think it’s incredibly awesome to realize

for example that the iron in the hemoglobin molecules running around your bloodstream

were actually fused deep in the heart of a massive star that blew up 8 billion years ago. And

so we are intimately connected with the cosmos, we are really star stuff. If we can learn to

step back and take that bigger look at who we are from a cosmic perspective, I hope it helps

us to realize that we’re all the same. We are all earthlings, and I think we should begin

trivializing the differences that we perceive among us that cause us to kill one another, to

wage war, to not take care of the planet in the way it should be. One of the ways you get

there is by knowing exactly what your path was, from stardust, to the planet, to life, to us, it’s

all connected”.

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