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== Directed panspermia ==

== Directed panspermia ==

In 1973, [[Francis Crick]], co-discoverer of [[DNA]], and [[Leslie Orgel]] proposed<ref>Crick, F. H. C., and Orgel, L. E. "Directed Panspermia," ''Icarus'', 19, 341 (1973).</ref> a new mechanism, which they called ''directed panspermia,'' to mitigate the hazards of transport and entry detailed above. They assume that an advanced [[civilization]] fired a brace of [[rocket]] [[missiles]], each laden with a [[payload]] of [[bacteria]] and/or [[blue-green algae]], in all directions. Crick and Orgel estimated that a payload of one [[metric ton]] could contain 10¹⁷ micro-organisms organized in ten or a hundred separate samples.

In 1973, [[Francis Crick]], co-discoverer of [[DNA]], and [[Leslie Orgel]] proposed<ref>Crick, F. H. C., and Orgel, L. E. "Directed Panspermia," ''Icarus'', 19, 341 (1973).</ref> a new mechanism, which they called ''[[directed panspermia]],'' to mitigate the hazards of transport and entry detailed above. They assume that an advanced [[civilization]] fired a brace of [[rocket]] [[missiles]], each laden with a [[payload]] of [[bacteria]] and/or [[blue-green algae]], in all directions. Crick and Orgel estimated that a payload of one [[metric ton]] could contain 10¹⁷ micro-organisms organized in ten or a hundred separate samples.

The theory has gained some attractiveness primarily by proposing to explain why so many life-forms on earth depend on the element [[molybdenum]], which is rare on earth but might not have been so rare on the planet of origin of these micro-organisms.

The theory has gained some attractiveness primarily by proposing to explain why so many life-forms on earth depend on the element [[molybdenum]], which is rare on earth but might not have been so rare on the planet of origin of these micro-organisms.