- January 27 – Scientists behind the climateprediction.net project, a distributed computing project run from Oxford University, announce that first results indicate a long term surface temperature increase due to global warming of between 2 and 11 degrees Celsius as a consequence of doubling carbon dioxide levels, with most of the simulations predicting a temperature rise of around 3.4 °C. The results are published in Nature.
- January 13 – Chinese paleontologists announce the discovery of fossils of Repenomamus robustus and Repenomamus giganticus, mammals that lived 130 million years ago. The fossil discoveries indicate that these mammals preyed on small dinosaurs. The results are published in Nature.
- February 17 – Two Ethiopian fossil skulls originally found in 1967 by Richard Leakey, Omo I and Omo II, are re-dated at 195,000 years old, making them the oldest Homo sapiens remains known. The results are published in Nature.
- December 15 – European and Canadian researchers announce the dating of flint artefacts from Pakefield, Suffolk, UK to around 700,000 years ago, representing the earliest unequivocal evidence for human presence north of the Alps. Results are published in Nature.
- January 14 – The Huygens probe is successfully sent into the atmosphere of Titan and returns science data to Earth via the Cassini orbiter. It survives the landing on the surface of Titan and sends pictures and other data for more than an hour afterwards.
- January 26 – ESA's SMART-1 begins sending back close range pictures of the lunar surface
- February 7 – NASA announce budget plans – in the announcement, they state that a mission to service the Hubble Space Telescope will not take place, and that a robotic mission to deorbit the telescope with a safe descent into an ocean will take place. The Jupiter Icy Moons Orbiter (Jimo) mission is also cancelled.
- February 12 – ESA successfully launch an Ariane 5 ECA carrying three satellites. The previous attempt to launch the new design of rocket, in December 2002, failed when the rocket deviated from its course minutes into the flight.
- July 4 – The Deep Impact spacecraft successfully observes the disintegration of its "impactor" section colliding with the comet Tempel 1. A large number of other telescopes also provide data on this event.
- February 3 – Ernst Mayr (b. 1904), evolutionary biologist.
- February 6 – Hubert Curien (b. 1924), former President of CERN and first chairman of ESA.
- February 10 – D. Allan Bromley (b. 1926), director of Yale's A. W. Wright Nuclear Structure Laboratory.
- March 6 – Hans Bethe (b. 1906), Nobelaureate in Physics (1967) for his discoveries concerning the energy production mechanism in stars.
- June 20 – Jack Kilby (b. 1923), Nobelaureate in Physics (2000) for his work on integrated circuits.
- June 20 – Charles David Keeling (b. 1928), first to make frequent measurements of atmospheric carbon dioxide (CO2) concentration, plotted on the Keeling Curve.
- August 21 – Robert Moog (b. 1934), pioneer of electronic music.
- August 31 – Sir Joseph Rotblat (b. 1908), physicist.
- October 28 – Richard Smalley (b. 1943), Nobelaureate in Chemistry (1996) for the discovery of a new form of carbon, Buckminsterfullerene.
- November 16 – Henry Taube (b. 1915), Nobelaureate in Chemistry (1983) for his work in the mechanisms of electron transfer reactions, especially in metal complexes.