J. William Schopf, professor of paleobiology at the University of California, Los Angeles, USA, will give a public lecture on "Ancient Life on Mars and Earth" on 20 September, at 18:00, in the Kastler Lecture Hall at the Adriatico Guesthouse. His presentation is part of the Sixth Trieste Conference on Chemical Evolution devoted to "First Steps in the Origin of Life in the Universe," which will take place at the ICTP between 18-22 September. The meeting will bring together many of the most renowned scientists in the field of astrobiology. Among them will be Stanley Miller, from the University of California, San Diego, USA, who in the 1950s synthesized simple organic molecules in a test-tube containing a mixture of the primeval gases of the Earth's atmosphere, and David McKay, of NASA's Johnson Space Center, Houston, USA, who four years ago claimed the first evidence of fossilized bacteria in a meteorite from Mars.