If Pluto was considered too small to be a planet, why does Mercury still hold planet status?

All of the above are incorrect in terms of the semantics of what "officially" makes a planet a planet. You need to look at the IAU (International Astronomical Union) definition of planet to see why Pluto is now defined as a dwarf planet

First, why does Pluto not fit the IAU planet defintion?

(1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Pluto fails in "c". Personally, I think "neighborhood" should be definined in terms of an orbital dynamics phase space since it never comes close to Neptune due to the 3:2 resonance of their orbits: my opinion and $3.95 will get you decaf latte at Starbucks. (Hmm... Neptune has not cleared Pluto out of ITS orbit either. . . maybe they know about some other icy bodies in Pluto's orbit?)

Pluto DOES meet the qualifications for a dwarf planet.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

Pluto's orbit is highly eccentric meaning that it doesnt follow the same orbit as the other planets. At certain times pluto will actually come within the orbit of neptune and be closer to the sun. Mercury is twice the size of pluto, but its orbit is elliptical just like the other 7 planets. This is one of the main reasons why mercury is still a planet. Pluto size and orbit were 2 of the main reasons why it was down graded to a dwarf planet.

Mercury is still a Planet because the Astronomy guilds didn't want to rock the boat too much. They are still split on Pluto and annexing a second Planet might have caused a rebellion. Imagine all those placard waving astronomers marching around the observatory chanting "We want Mercury and Pluto."

Scary!

1. Mercury is twice the size of Pluto

2. Mercury has cleared its orbital path around the sun of virtually all debris (asteroids).

3. Mercury's orbital path is much less eccentric, meaning it is closer to a circle than an oval like pluto's.

4. Pluot 's orbital path does not lie in the same plane as the rest of the solar system it is inclined by 9 degrees while the other eight are roughly flat paths similar to the rings of saturn.

Pluto is only about 1/2 the size of Mercury, so there's no "discrepancy" there.

Pluto is the same as it always has been (ok, the same as it's been the last 4 billion years or so) -- we just changed how we define it. No big deal :) Science changes definitions to make things more clear (or in some cases to make them more confusing!) all the time.

It's not only Pluto's size that caused its "demotion". Also to be considered is the extremely irregular orbit. First of all, the orbit has a very large tilt to the equatorial plane of the Solar System. Secondly, Pluto's orbit also crosses that of Neptune, so far a part of the Plutonian"year", it is closer to the Sun than Neptune. More than size, this characteristic, closely resembling asteroids, is the cause for Pluto's new designation.

So we still have a few small planets in our solar system . Maybe scientists don't want our solar system to be like a worthless , small , piece of sh*t with only a little bit of planets . Why do you think the U.S. got California and Texas from Mexico and Alaska from Canada .

Mercury is a lot bigger than Pluto.

Pluto's planetary status wasn't jeopardized by it's size, but it's content: gas and ice.

I'm guessing because...

MAYBE MERCURY'S LARGER THAN PLUTO?!