Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin
There may be as many as 2 million asteroids larger than 1 kilometre (0.6 miles) in size and 25 million asteroids larger than 100 metres (100 yards). About three-quarters of a million are known and catalogued. Why so many small asteroids? The answer is: 'because there were so many to start with'. There were so many asteroids confined into a restricted area of the solar system that collisions were inevitable. The fragments from the collisions between large asteroids became the numerous smaller asteroids.
Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin So, some of the soil in your window box or garden – just a little – is from Mars; the carrots you eat contain a sprinkling from the Red Planet. And, just as the Earth is sprinkled with Martian soil, so Mars is sprinkled with the soil of our own planet.
Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin Mars is the most Earth-like planet of the solar system. It is considerably smaller, half the diameter of the Earth. It is much colder and drier, but it started its life in the same way as the Earth did, 4.6 billion years ago, warm and wet, with a thick atmosphere and abundant water.
Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin The collision was a glancing blow, and left the Earth rotating once every five hours. The Moon ended up orbiting the Earth much closer than it does today. The tidal forces between the two bodies locked the Moon so that the same hemisphere faces the Earth; the dissipation of energy by tidal forces acting over billions of years took energy from the orbit of the Moon and the rotation of the Earth. The Moon retreated to its present distance: it is still retreating at 4 centimetres (2 inches) per year. The Earth slowed down, the day lengthening from five hours to its present-day value of twenty-four hours: it is still slowing down.
Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin Eventually, even its liquid iron core will solidify and convection will seize up. Our planet's magnetic field will die away completely and permanently. Unlike the temporary loss of magnetic field during the switchovers, this permanent loss will be catastrophic. Unimpeded, the Sun's particles will scour away the atmosphere. With no air pressure to keep water molecules from escaping from seawater, the oceans will boil away, rainfall will cease, the land will dry out. Earth will have lots its equanimity and turned into Mars.
Excerpt from The Secret Lives of Planets: Order, Chaos, and Uniqueness in the Solar System, Paul Murdin |
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