States from 1992 to 1996. However, the Taurus would be outsold and dethroned by the Toyota Camry starting in 1997, which became the best-selling car in the United States for the rest of the decade and into the 2000s. Ford also introduced the Ford Explorer, with the first model being sold in 1991. Ford's Explorer became the best-selling SUV on the market, outselling both the Chevy Blazer and Jeep Cherokee. Japanese cars continued to be highly successful during the decade. The Honda Accord vied with the Taurus most years for being the best-selling car in the United States during the early decade. Although launched in 1989, the luxury brands Lexus and Infiniti began car sales of 1990 model year vehicles and saw great success. Lexus would go on to outsell Mercedes-Benz and BMW in the United States by 1991 and outsell Cadillac and Lincoln by the end of the decade. SUVs and trucks became hugely popular during the economic boom in the decade's second half. Many manufacturers that had never built a truck before started selling SUVs. Fabrication during the 1990s became gradually rounder and ovoid, the Ford Taurus and Mercury Sable being some of the more extreme examples. Safety features such as airbags and shoulder belts became mandatory equipment on new cars. Science Physicists develop M-theory. Detection of extrasolar planets orbiting stars other than the sun. In the United Kingdom, the first cloned mammal, Dolly the sheep was confirmed by the Roslin Institute, and was reported by global media on 26 February 1997. Dolly would trigger a raging controversy on cloning, and bioethical concerns regarding possible human cloning continue to this day. Human Genome Project begins under the leadership of Francis Collins. DNA identification of individuals finds wide application in criminal law. Brazil, United States, United Kingdom, Russia and The Netherlands established their own national DNA database. Hubble Space Telescope was launched in 1990 and revolutionized astronomy. Unfortunately, a flaw in its main mirror caused it to produce fuzzy, distorted images. This was corrected by a shuttle repair mission in 1993. Protease inhibitors introduced, allowing HAART therapy against HIV; drastically reduces AIDS mortality. NASA's spacecraft Pathfinder lands on Mars and deploys a small roving vehicle, Sojourner, which analyzes the planet's geology and atmosphere. The Hale–Bopp comet swings past the sun for the first time in 4,200 years in April 1997. Development of biodegradable products, replacing products made from polystyrene