Scienceblog

Both objects will go far outside the lunar orbit. This weekend, two asteroids the size of skyscrapers are speeding toward Earth. One will make its closest approach on Friday, July 29, while the other will pass by on Saturday (July 30). NASA estimates that the first asteroid, 2016 CZ31, will come by at a speed of 34,560 mph (55,618 km/h) on Friday about 7 p.m. ET (23:00 GMT). The asteroid, which is roughly as wide as a 40-story skyscraper is tall, is thought to be 400 feet (122 meters) across at its widest point. The asteroid will pass around 1,740,000 miles (2,800,000 kilometers) from Earth, or more than seven times the typical distance between Earth and the moon, safely avoiding our planet. The next near encounter of this space rock with Earth is expected for January 2028, according to NASA. A second, bigger asteroid will pass by Earth on Saturday, albeit it will be further away. At its widest visible point, that asteroid, 2013 CU83, is roughly 600 feet (183 meters) across. It will pa...

Currently, oxygen makes up around 21% of Earth's atmosphere. But it took a while for the atmosphere on our planet to reach the point where it is now breathable. Methane, hydrogen sulfide, and carbon dioxide, among other gases, were among the initial mixtures to accumulate as a thick layer surrounding our cooling planet 4.6 billion years ago. These were turbulent times; in addition to the volatile ingredients swirling within the Earth, a regular barrage of frigid rocks from the inner Solar System kept the supply of new material flowing. Larger impacts periodically heated the surface, boiling any moisture that had accumulated and maintaining the hot mucky environment. But there was also enough of nitrogen in the form of ammonia in that constant stream of minerals falling from the sky. When did oxygen first enter the atmosphere of Earth? We still don't know a lot of the specifics. We are unsure of the exact amount of nitrogen that the early mineral rain delivered to our planet, fo...