You may have seen news headlines referring to an asteroid possibly to hit or "threatening" Mars. It is true that a space rock, about 164 feet across, could hit the Red Planet on January 30. The event isn't a certainty, however, and if it does happen Mars will survive relatively unscathed. At first the odds of an impact were said to be 1 in 75. Recent analysis of other observations has refined the asteroid's orbit and the odds are now at 1 in 25. Astronomers will continue to narrow the odds between now and the end of January and will know in advance and for certain whether Mars will take a hit.
If the asteroid were to hit Mars the result would be a large crater (perhaps half a mile in diameter) but the planet as a whole would be largely unaffected -- Mars is half the size of Earth but it's still much bigger than the house-sized asteroid (if you have a really big house). In fact many space scientists hope the collision takes place because it would provide insight into the makeup of Mars and the dynamics of such a large event. Several spacecraft are currently in orbit around Mars and could make unprecedented observations of the impact and/or its aftermath. The two still-functioning Mars rovers would also make observations. Only space-based and, perhaps, the largest of ground-based telescopes have any chance of seeing the collision, if it happens at all.
Better Mars than us: The energy released by a 164-foot asteroid hitting Earth would cause untold destruction if it impacted anywhere near a population center. In June of 1908 an object believed to be of about the same size as the one we are discussing exploded over Siberia with a yield equivalent to a 10- to 15-megaton nuclear device. The "Tunguska Event" felled an estimated 80 million trees over 830 square miles. Today's tracking of the Mars-bound rock reminds us that there are still dangers "out there" of which we need to be aware and with which we may one day need to cope.