Exploratour - Evolution of the Solar System
A star that is newly born like this is in a childhood phase called the T-Tauri phase. During its T-Tauri phase, when the Sun first started shining, it was not very bright. But it was very powerful, nevertheless, and spit out a stream of particles into space. The sun still spits out this stream of particles, today, in a much less powerful form. It is called the "solar wind".
But the force of T-Tauri "wind" was probably enough to take away of whatever atmosphere had been gathered from the solar nebula around Mercury, Venus, Earth, and Mars.
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