Dear MEL Topic Readers,
Mercury: The planet that shouldn't exist
Mercury is the nearest planet to the Sun, only 0.4 astronomical units
(AU) away, 40% of the distance from the Sun to Earth. It is the fastest planet
to orbit the Sun, taking only 88 days to orbit the Sun at a speed of nearly 47
kilometers per second. Mercury’s surface temperatures are both extremely hot
and cold, between 430°C and -180°C, because it’s too close to the Sun and it
spins so slowly, taking 59 Earth days for one rotation. Mercury formed about 4.6
billion years ago, like others, when gravity pulled swirling gas and dust
together. It is the smallest planet in our solar system, only slightly larger
than our moon, and the second densest planet after Earth, because Mercury’s
core makes up about 85% of its radius while Earth, Venus, and Mars all have iron-rich
cores that make up about half of their radius. Yet it is still uncertain why
Mercury orbits so close to the Sun and how its dense structure was formed. This
November, a joint European and Japanese space mission is due to enter orbit and
is expected to reveal where Mercury came from.
Read the article and learn about the smallest planet in our solar
system.
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