Let’s try and catch up with the elusive 'swift messenger' called MERCURY that races around the Sun at ~48 kilometres per second. Let’s give Mercury the once over and see if it’s your idea of home sweet home:
· 450 degrees C by day (lasting 59 Earth days)…..phew, that’s one long scorcher of a day!
· Minus 170 degrees C at night……brrrrr!· virtually no atmosphere…..o’oh!
· no moon – there’s nothing to regulate
· a weak magnetic field against cosmic radiation – danger!
· BYO water, except possible ice at the poles
· no seasons like Earth
· A highly elliptical orbit, taking 87.9694 Earth days, that isn't really centred around the Sun
Mercury doesn't sound too Earth-like to me, but there's more.....we haven't mentioned its rotation. Mercury is extremely difficult to observe because it lies within 28 degrees of the glaring Sun and being closer than Earth, often presents only a thin crescent or a dark side to us. Apparently it presents the same face to Earth at the best position for observation, so until 1965 we thought that its rotation was locked to the Sun but with the aid of Doppler radar it was found that its rotational period was 58.6461 days, making 3 rotations for every 2 orbits.
Did you get that? Mercury does its own loopy thing under the control of the Sun and yet remains synchronised with itself! Its rotation synchronises with its orbit at the ratio 3:2, to an accuracy of 99.99972% : only 43.2 seconds difference in 176 Earth days (1 Mercurial day takes 2 orbits). At the same time it appears to also synchronise with observations from Earth - keeping us guessing for thousands of years.
How about that!
Does that sound like the result of an uncontrolled 'big bang'?
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