Final answer:
1. Jupiter and 2. Mars are the planets that reside in the middle region of the solar system. Uranus and Neptune, being outer or ice giants, are not in the middle region but farther away.
Step-by-step explanation:
The planets that reside in the middle region of the solar system are 1. Jupiter and 2. Mars. While the gas giants Jupiter and Saturn have overall compositions similar to that of the Sun and have been explored extensively by missions such as Voyager and Cassini, Mars is known as a terrestrial planet.
Uranus and Neptune are considered outer planets or ice giants and lie beyond the middle region of the solar system. In terms of mass, Jupiter is 318 times more massive than Earth, and together with Saturn, they have extended mantles of liquid hydrogen.
Uranus and Neptune are depleted in hydrogen and helium relative to Jupiter and Saturn, and each giant planet has a core of ice and rock, but these are not considered middle region planets.