"Planetary Defense" is the proper term for preventing asteroid impacts to the Earth. "Planetary Protection" is the process of preventing biological contamination of other solar system objects, and also avoiding adverse effects to the environment of the Earth due to the introduction of extraterrestrial material. I hope this information is useful.
Sincerely, Catharine A. Conley, NASA Planetary Protection Officer
Most of my stories are about planetary, defense, but here is one that get's to planetary protection.
Then tis interesting new article on looking for DNA on Mars:
J. Craig Venter may have just started a race to discover alien life on the Red Planet.
Two high-profile entrepreneurs say they want to put a DNA sequencing machine on the surface of Mars in a bid to prove the existence of extraterrestrial life.
Venter said researchers working with him have already begun tests at a Mars-like site in the Mojave Desert. Their goal, he said, is to demonstrate a machine capable of autonomously isolating microbes from soil, sequencing their DNA, and then transmitting the information to a remote computer, as would be required on an unmanned Mars mission. (Hear his comments in this video, starting at 00:11:01.) Heather Kowalski, a spokeswoman for Venter, confirmed the existence of the project but said the prototype system was “not yet 100 percent robotic.”
Meanwhile, Rothberg’s Personal Genome Machine is being adapted for Martian conditions as part of a NASA-funded project at Harvard and MIT called SET-G, or “the search for extraterrestrial genomes.”
Christopher Carr, an MIT research scientist involved in the effort, says his lab is working to shrink Ion Torrent’s machine from 30 kilograms down to just three kilograms so that it can fit on a NASA rover.
Looking for DNA on Mars won’t be easy. A robot would have to scoop up soil and prepare a sample automatically. The sequencing machine would need to work in cold temperatures and in a very thin atmosphere made mostly of carbon dioxide. Martian genes might also be different from those in the bodies of terrestrial animals, perhaps being made up of different chemical building blocks.
Discovering and sequencing extraterrestrial life would be an immense scientific prize. Sequencing could reveal whether life evolved in similar ways on both Earth and Mars or, perhaps, moved between the planets. During a series of massive space collisions around four billion years ago, the two bodies exchanged about a billion tons of rocks and debris.
Venter also said it might be feasible in the future to reconstruct Martian organisms in a super-secure laboratory on Earth, using just their DNA sequence. The idea would be to use the DNA data to rebuild their genomes and then inject those into an artificial cell of some kind. It’s an idea he calls the “biological teleporter.”
And perhaps they'll find some, as:
The UK researchers say that tiny algae-like fossils found in meteorite fragments that landed in Sri Lanka last year can’t have originated on our planet, according to the study published in the Journal of Science.