Mars mosaic

Abstract

Mars is coooler, clearer, and drier than the Red Planet was a couple of decades ago, according to new data released last week, which include this collection of the first Mars opposition images taken since the Hubble Space Telescope (HST) was repaired in December 1993. Related spectroscopic studies also reveal that the abundance of ozone in Mars' atmosphere has increased threefold at equatorial levels. “Mars is in a very different climate regime than it was a couple decades ago,” when the Viking spacecraft visited the planet, says Steven Lee of the University of Colorado at Boulder. What's more, the average global temperature has dropped 20 K since the mid‐1970s, largely due to the settling of dust particles, which absorb sunlight and warm the atmosphere. In fact, Mars is about 3 times less dusty than it was during the Viking visit. Lee notes, “We just happened to visit Mars when it was dusty, and now the dust has settled out.” Scientists estimate that Mars' climate has been very stable over the past 1.5 years. Observations of Mars' atmosphere may help shed light on processes at work in Earth's atmosphere, scientists say.