Extraterrerstrial Life - Have They Been Here? Will We Visit Them? Do They Exist At All?

Let us first talk about the Universe and what we know about it so far.

Cosmos or the Universe as we call it today is believed to consist of more than 150 billions of galaxies.

Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars, all orbiting the galaxy's center of mass. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The Sun is one of the stars in our Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.

After galaxies outside the Milky Way were found to exist, initial observations were made mostly using visible light. The peak radiation of most stars lies here, so the observation of the stars that form galaxies has been a major component of optical astronomy. It is also a favorable portion of the spectrum for observing ionized H II regions, and for examining the distribution of dusty arms.

The dust present in the interstellar medium is opaque to visual light. It is more transparent to far-infrared, which can be used to observe the interior regions of giant molecular clouds and galactic cores in great detail. Infrared is also used to observe distant, red-shifted galaxies that were formed much earlier in the history of the universe. Water vapor and carbon dioxide absorb a number of useful portions of the infrared spectrum, so high-altitude or space-based telescopes are used for infrared astronomy.

The first non-visual study of galaxies, particularly active galaxies, was made using radio frequencies. The atmosphere is nearly transparent to radio between 5 MHz and 30 GHz. (The ionosphere blocks signals below this range.) Large radio interferometers have been used to map the active jets emitted from active nuclei. Radio telescopes can also be used to observe neutral hydrogen, including, potentially, the non-ionized matter in the early universe that later collapsed to form galaxies.

Ultraviolet and X-ray telescopes can observe highly energetic galactic phenomena. An ultraviolet flare was observed when a star in a distant galaxy was torn apart from the tidal forces of a black hole. The distribution of hot gas in galactic clusters can be mapped by X-rays. The existence of super-massive black holes at the cores of galaxies was confirmed through X-ray astronomy.

What kinds of efforts have been done by our major space exploration companies NASA and ESA?

Have their efforts given us any answers to the initial questions asked here?

Both organizations have launched several space based observatories enabling us to get an understanding of our own solar system, galaxy and the universe. But, so far, there has not been any scientific proof of life from these observations.

Mars space missions have given us some answers that there is a probability for existence of frozen water, hence some potential for bacterial life forms.

NASA alone and in collaboration with ESA have launched several space based observatories through the last two decades in order to give us the opportunity to see past the noise on earth and to look into the other invisible spectra of energy that we can not see in the visible light spectra.

NASA launched a space program in 1990 with 4 stages in it.

First, we had the launch of the Hubble space telescope launched in 1990, which was destined to orbit the earth at 569 kilometers. This observatory had equipment to observe in the visible, near infrared spectrum of light, and have spectrograph and a wide field and planetary camera onboard. This was a joint venture with ESA.

The second stage of the program was the launch of the Compton Gamma Ray Observatory at April 5th 1991. This observatory had equipment onboard to observe the electromagnetic spectrum. The mission ended in June 4th 2000, when the observatory was deorbited.

The third stage of the program was the launch of Chandra space telescope in July 23rd 1999. This observatory is expected to last through 2009 and maybe a bit longer.  Chandra is observing the x-ray signals and is orbiting around 139000 kilometers above the earth, which is about a third of the distance to the moon.

The fourth stage of this program was the launch of the Spitzer Space Telescope destined to observe the infrared, heat, radiation. The launch was on August 23rd 2003 and the expected lifespan of 5 years is already exceeded. It is still operational after some minor adjustment done recently. The observatory is gradually moving away from us with a speed of 15 million kilometers per year from its original orbit behind the earth, seen from the sun.

NASA has just recently launched on March 6th 2009, the Kepler Space telescope. This telescope is designed to search for Earth-like planets orbiting other stars. Using a space photometer developed by NASA, it will observe the brightness of over 100,000 stars over 3.5 years to detect periodic transits of a star by its planets.

The Kepler Mission has a much higher probability of detecting Earth-like planets than the Hubble Space Telescope, since it has a much larger field of view (approximately 10 degrees square), and will be dedicated for detecting planetary transits.

Discovering planets comparable to Earth is expected to take three years or longer with this mission. Kepler is not in an Earth orbit but in an Earth-trailing solar orbit.

The use of these telescopes in collaboration to make pictures of galaxies or stars within a multi range spectrum enables us to get the fantastic pictures we can see at NASA web site f.inst. It also enables us to take observations of various generations of stars and galaxies.

Several other space based observatories have been launched into space in the last decades or so.

Wilkenson Microwave Anisotropy Probe (WMAP) was launched June 30th 2001 to observe cosmic glow, temperature fluctations with a sensitivity of 0.00001 degrees celcius. It claims to have made observations from when the universe was only 380.000 years old. The universe is assumed to be 13-14 billion years old. The observatory is placed in Lagrange point L2, behind the earth (1.5 kilometers from earth).

Solar and Heliospheric Observatory Satelite - SOHO launched December 2nd 1995 as a joint venture with NASA and ESA. SOHO currently continues to operate after over ten years in space. In addition to its scientific mission, it is currently the main source of near-real time solar data for space weather prediction. The observatory is located at the Lagrange point L1 between the earth ands the sun.

The Global Geospace Science (GGS) WIND satellite, a NASA science spacecraft launched on November 1, 1994 and Advanced Composition Explorer (ACE), are two other spacecrafts currently in the vicinity of the Earth-Sun L1 point, around 1.5 kilometers from the earth.

The WIND was deployed to study radio and plasma that occur in the solar wind and in the Earth's magnetosphere.

The objective of ACE is to study matter in situ, comprising energetic particles from the solar wind, the interplanetary medium, and other sources. Real-time data from ACE is used to improve forecasts and warnings of solar storms. The observatory was launched August 25th, 1997.

The Galaxy Evolution Explorer (GALEX) was launched on April 28th 2003.  This observatory was designed for observations of the ultraviolet far UV spectrum of energy.

STEREO (Solar TErrestrial RElations Observatory) is the third mission in NASA's Solar Terrestrial Probes program (STP). This two-year mission, launched October 2006, will provide a unique and revolutionary view of the Sun-Earth System. The two nearly identical observatories - one ahead of Earth in its orbit, the other trailing behind - will trace the flow of energy and matter from the Sun to Earth. They will reveal the 3D structure of coronal mass ejections; violent eruptions of matter from the sun that can disrupt satellites and power grids, and help us understand why they happen. STEREO will become a key addition to the fleet of space weather detection satellites by providing more accurate alerts for the arrival time of Earth directed ejections with its unique side-viewing perspective. On January 24, 2009 the two STEREO spacecraft reached 90 degrees separation, a condition known as quadrature. Since the two STEREO spacecraft went into orbit around the Sun at the beginning of 2007, they have been slowly drifting apart from Earth, and from each other. Ahead has been drifting at an average rate of 22 degrees per year in front of Earth, and behind has been drifting at the same rate in the opposite direction. After two years in solar orbit, the two spacecraft have finally reached quadrature.

ODIN was launched in February 2001 with a two-year life expectancy, the Swedish Space Corporation's Odin satellite has a dual purpose: to study star formation and the early solar system, and to study Earth's atmosphere, where it will research the mechanisms behind the depletion of the ozone layer and the effects of global warming.

SWAS was launched into low Earth orbit in December 1998; the Submillimeter Wave Astronomy Satellite (SWAS) was a two-year NASA mission to enhance understanding of star formation by studying the composition of interstellar clouds and the means by which they collapse.  SWAS provided the most precise measurements of water vapor in interstellar clouds and established the tightest limits on the maximum amount of molecular oxygen that might be in these clouds.

The Infrared Astronomical Satellite (IRAS) was the first space-based telescope to attempt a complete survey of the sky at infrared wavelengths.  IRAS detected some 350,000 sources in the mid-infrared (5-40 microns) and far-infrared (40-100 microns), increasing the number of known astronomical objects by about 70%. Among IRAS's discoveries were the first known disk of dust around a star (Vega), six new comets, and a population of "ultraluminous infrared galaxies" that are much brighter at infrared than optical wavelengths

IRAS's successor was the European Space Agency's Infrared Space Observatory (ISO), which operated from November 1995 to May 1998. ISO observed in the range from 2.5 to 240 microns with greater sensitivity and resolution than its predecessor, and made the startling discovery that water vapor is a common and important part of the interstellar medium. The satellite found water in the vicinity of stars both at the beginning and end of their lives, in sources close to the center of the galaxy, and in the atmospheres of planets in our Solar System. ISO also discovered that most ultraluminous galaxies appear to be powered by starbursts rather than by black holes.

Future planned launches of space based observatories are:
Planck Satellite will be launched in spring 2009.

Herschel Space Observatory comes in spring 2009. Herschel will cover 1000 times more frequency "real estate" than SWAS, which observed spectral lines at five specific submillimeter wavelengths: those of water, isotopic water, molecular oxygen, neutral carbon, and isotopic carbon monoxide.

James Webb Space Communication Satellite launches in 2013 or later. This observatory will observe the infrared electro magnetic spectrum and the visible part.

Then there is the Gaia Probe for which there is no date set yet.

Summary
The answer to our initial questions, no we have not found any scientific evidence of life forms, at least anything with intelligence close to or beyond ours.

This is not due to the fact that there is no chance for life forms within our galaxy or beyond, but rather our technological limitations and maybe also intellectual limitations to search efficiently for life forms.

I am a profound believer in that there are life forms apart from us in our universe or cosmos, somewhere. Whether we will be able to communicate with these before our earth goes to extinction is another question I am more doubtful of.

So far we have only been able to look close into our own galaxy, and not been able to thoroughly examine other galaxies. We might have a few thousands of years to search at the maximum, not limited by that our sun will swallow us (it is more than a billion years to that event), but the exploiting by humans, which makes our time here on earth limited by the fact that there is not enough resources to go around with our ever so expanding population.