I learned that mercury is the second smallest planet (which is now actually the smallest pla
net because Pluto is no longer a planet), I learned that the fist americain space craft mission to mercury was by mariner 10 in 1974-1975. Mercury has many craters and looks much like our moon. Mercury also had a liquid core, the crust was also liquid, the crust solidified before the core did so it was still molten rock, when the core solidified also it contracted which is why some scientists think that there are so many mountains on mercury, but that is just a hypothesis.
I learned that Venus is called earths twin because of their similar size and mass. The former Soviet Union landed the first probe on Venus in 1970, it was called Vanera 7. It stopped working within 1 hour though because of high pressure and heat. Between 1990 and 1994 the Magellan probe from the u.s used its radar to collect images of 98% of Venus’s surface and make the most detailed maps yet. Also I learned that venus temperature on the surface is between 450 and 475 degrees Celsius.