Brace yourself for a flight of the imagination.  Exoarchaeology, sometimes known as xenoarcheology, is a hypothetical branch of archaeology that looks for the physical signs of past and present alien cultures.

Although this may sound far fetched and not a subject to pursue in these financially tight recessionary times the subject can be developed through careful thought. It rests of course on the totally unproven assumption that there is intelligent life in the universe beyond the planet earth.

Percival Lovell could be called the father of exoarchaeology. Lovell was an extremely rich American who left a diplomatic areer in 1893 at the age of 38 to devote the remaining 23 years of his life to planetary astronomy. Lovell was particularly interested in the canals on Mars. In 1877 the Italian astronomer Giovanni Schiaparelli reported long filament like structures on the surface of Mars which he called canali. Lovell published three influential books, Mars (1895), Mars and Its Canals (1906), and Mars As the Abode of Life (1908) which interpreted the canals as evidence for intelligent life on Mars. Lovell speculated that a sophisticated society was tapping the dwindling water supplies of the Red Planet by directing seasonal water from the polar ice caps.

Lovell made an important contribution to the public imagination.His work inspired H G Wells to write the classic story of alien contact, the War of the Worlds. Since that time numerous authors have explored the issues involved in the quest and discovery of alien civilisations.  Many of their topics deserve consideration because we know so little about exoarchaeology.

What would be the motive driving an alien civiilisation that left artifacts for us to find?

Does a civilisation need to leave its home planet and leave artifacts?

Do civilisations even need to have a physical form at all?

Could an alien civilisation be so advanced that we are already under observation without our knowledge?

What are we to make of folklores and myths that talk of people beyond the stars?

Many exoarchaeologists are content to look for evidence of alien civilisations on Earth. Conceptionally this is one of the easier forms of exoarchaeology and has the potential to reveal astonishing results. Their investigations have led practitioners to study UFO encounters, The alignments of the Pyramids and ancient monuments to the stars on the basis that a superior intelligence must have helped with the design and think long and hard about the amazing Nazca lines in Peru. The Nazco lines depict huge animal and natural shapes that seem only possible if designed from space.Statistically it is unclear why a alien civilisation should take an interest in Earth. These studies rest on convenience and a deep seated interest in anthropmorphism.

Within the solar system exoarcheologists can look for structures that might have been made by a civilisation. Naturally, this work led to an investigation into unusual geological features. An alleged bridge structure on the moon in 1953 and a series of obelisk like structures again on the moon in 1966. Like the canals on Mars both features have been discredited. A rigorous search of the lunar surface for artifacts might even be viable. Because it has no atmosphere aerial photographs of the lunar surface are particularly sharp.

If  physical objects can not be found the next line of enquiry should in be the elecromagnetic spectrum  This can in principle give evidence of life and civilisations beyond the Earth.  The studies can be outgoing, in the sense that  a probe such as Pioneer 10 with detail of our civilisation was set out to wait for a reply, or passive as in the case with tthe SETI  program in which we search for a signal to come to us. Active searches have take place since the pioneering work for Frank Drake at the University of Cornell in 1960. The scientists working on the program have developed sophisticated tests to distinguish between a signal of natural origin and one contrived by an intelligent civilisation. The later has a much greater information content.  

As yet the listening scientists that have not found an intelligent signal. Although their studies are young compared to the age of the universe their lack of success is forcing a rethink. Either life is extremely uncommon in the universe or the searhc is ill founded. Scientists now think that a generalised search for intelligent life looking for a signal to come to us is inefficient and would be recognised as such by an advanced civilisation. Our era of electoric analogue broadcasts in already coming to an end,

Scientists think that a smart civilisation would make contact using a different strategy. An efficient path would be to send out a large number of probes each heading for a likely place where life might exist. The destinations would be solar systems where life might evolve. Once in a solar system the probes would align at static points where they could maintain their position with minimum energy expenditure. These points are known as Lagrangian points in honour of the mathematician Lagrange who discovered them. Lagrange found that there were certain points where the gravitational pull of the Earth and the Moon, or the Sun and Jupiter exactly cancel out. These exist in any three body gravitational system.

When the technology is ready exoarcheologists should seek out extra terrestial solarsystems and closely examine their Lagrangian points.