Word: planet
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Dates: during 2000-2009
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...then again, there aren't a lot of things like NASA's Spirit and Opportunity Mars rovers, the robotic ships that landed on the Red Planet five years ago this month with an expected lifespan of 90 days and yet have chugged along ever since - surviving paralyzing cold, blinding dust and long periods without sun, all of which occasionally left them silent and still, but only until conditions improved and they shook off the dust, stirred to life and puttered off to do more work. So far, Spirit and Opportunity have beamed home a quarter of a million images...
...goodly distance - 35 million miles in 2003 - which means that the rovers needed seven months to get where they were going. Spirit landed first, bouncing down in a swaddle of air bags in Mars' Gusev Crater. Opportunity followed three weeks later, landing on the other side of the planet in what is now known as Eagle Crater...
...spots were chosen for a very good reason. Despite the caps of ice in Mars' polar regions and the deposits of ice thought to lie beneath the soil, the planet is a desiccated place. But that doesn't mean Mars wasn't once wet, and its topography - scarred with what appear to be ancient river channels and dry seabed - suggests that the planet once fairly sloshed with water. If you want to find signs of ancient life, the key is to follow that water - or at least the places it used...
...leap second will be added to atomic clocks around the world to realign Coordinated Universal Time (UTC), the international standard for atomic clocks, with Earth's rotational period. The reason for the intermittent mismatch between these two measurements lies not with the clocks but with the movement of the planet, which is decelerating at an average rate of two milliseconds...
Space dust, magnetic storms, solar winds and the Earth's atmosphere all create drag, which slows down the planet. Even the amount of snow covering the polar ice caps adds to the rotational lag. But one of the main obstacles is tidal friction. Because the gravitational pull between the moon and the Earth is not uniform, the tidal force stretches the Earth - core, mantle, crust, oceans and all - producing bulges. The Earth's rotation pushes the tidal bulge slightly ahead of the Earth-moon alignment; the moon's gravity, however, yanks the bulges back to keep them in line. This...