Is the surface of Pluto like that of the Moon?

 Scientists assumed Pluto was a dead rock just like Earth's Moon. Instead, NASA found a bizarrely active world where towering mountains of solid ice float on churning nitrogen glaciers.

The Moon is a classic geologically dead body. Covered in a powdery layer of shattered rock and dust called regolith, its surface has been locked in time for billions of years. With no atmosphere, no weather, and a cooled interior, the only thing that changes the lunar landscape is the occasional impact of a meteor. Every crater from the last three billion years remains exactly where it formed.

Despite surface temperatures hovering around -390°F (-234°C), Pluto is a dynamic world constantly resurfacing itself. The strongest contrast is a vast, heart-shaped glacier of frozen nitrogen known as Sputnik Planitia. This region is nearly devoid of impact craters. Heat slowly radiating from Pluto's interior warms the bottom of the nitrogen ice layer, causing it to bubble up and sink back down in giant, polygonal convection cells—much like a slow, freezing lava lamp. This continuous churning paves over new craters, keeping the surface looking brand new.

Bordering these smooth nitrogen plains are jagged mountain ranges, such as the Norgay Montes, that rise up to 20,000 feet high. While the Moon's mountains are made of silicate rock pushed up by ancient impacts, Pluto's ranges are blocks of solid water ice. At Pluto's extreme temperatures, water ice becomes as hard as granite, allowing these colossal blocks to ride atop the denser, softer nitrogen below.

Unlike the monochromatic gray of the Moon, Pluto is highly varied in color. Large stretches of its surface are stained a deep reddish-brown by tholins—complex organic molecules formed when ultraviolet sunlight breaks down the methane and nitrogen in Pluto's thin, hazy atmosphere.

NASA's New Horizons probe captured this high-resolution true-color image of Pluto in 2015, revealing the bright, crater-free nitrogen ice glacier of Sputnik Planitia on the right alongside older, cratered terrain stained with reddish-brown tholins. Source: Wikimedia Commons.

Is Pluto still a planet, or do astronomers call it a dwarf planet?

When it was discovered in 1930, Pluto was considered to be the ninth planet of the Solar System. It’s quite tiny, though: about half the size of our own Moon.

(Pluto is bottom left)

But over time, astronomers began to realise just how many similar objects there are out there beyond Neptune, in what is called the Kuiper Belt (which is kind of similar to the Asteroid Belt between Mars and Jupiter). Dozens, maybe hundreds or even thousands of them.

So if we are calling Pluto a planet, putting in the same category as Earth, Mars, etc., then there’s potentially a vast number more which should be added to the traditional list of planets. That’s not very convenient or clear.

So in 2006 the International Astronomical Union decided to define exactly what we mean by the word ‘planet’. An upshot of that was that Pluto didn’t fully qualify and came to be redefined as a ‘dwarf planet’. That is,

• it’s a round object and it’s orbiting the Sun just like a planet,
• however, it’s very small, more like the size of a moon or asteroid,
• and as such, it’s not big enough (gravitationally) to ever carve out an orbit all to itself like any big planet would.

Pluto is now just one of several dwarf planets that have been identified, including Haumea, Makemake, Eris and Ceres.

A couple of interesting facts about Pluto:

Pluto’s 248-year elliptical orbit around the Sun sometimes brings it closer to the Sun than Neptune’s orbit.

Pluto has a surprisingly big satellite (moon), called Charon. In effect, it’s a binary system.

Why does Pluto have mountains?

 

The reasons are mean, the place where pluto lives has its own rules, it is very cold here, water ice becomes bedrock.

It gets frozen harder and meaner than stone on Earth. It is a place of giants mountains, jagged blocks of this water ice-They are not pushed up by colliding continents.

Frozen nitrogen, a great flat sea of it.

A glacier. A thing called Sputnik Planiti. A moving sheet of softer ice-puts great heft on the edges of its basin.

It shoves against the water ice crust-A thing that is unyielding, cracks and pushes colossal blocks miles into cold air.

There are other peaks.

Great mean mounds on the plains, these things are likely cryovolcanoes-They spew a slushy, icy mix from gut of Pluto, no hot lava.

Why is Pluto no longer considered a planet?

 The reason that Pluto is no longer a planet is not because of its size. In fact, it passes the test for "size" (mass).

The definition of 'planet' was made more strict. It is as following:

1. Massive enough to be round. Very massive bodies have so much gravity that they crush down any irregular edges towards their centre, and so become ball-like.

2. The primary object orbiting the Sun. For instance, the Moon orbit's the Sun, but it does so by orbiting the Earth. The Earth is the primary object orbiting the Sun.

3. Has cleared it's own orbit. Planets clear their orbits of debris/asteroids (by attracting them with their gravity).

Pluto passes 1 and 2, but has not passed 3. It has not cleared it's orbit of debris.

Objects like Pluto are called Dwarf Planets.

Why is Pluto no longer considered a planet?

 The reason that Pluto is no longer a planet is not because of its size. In fact, it passes the test for "size" (mass).

The definition of 'planet' was made more strict. It is as following:

1. Massive enough to be round. Very massive bodies have so much gravity that they crush down any irregular edges towards their centre, and so become ball-like.

2. The primary object orbiting the Sun. For instance, the Moon orbit's the Sun, but it does so by orbiting the Earth. The Earth is the primary object orbiting the Sun.

3. Has cleared it's own orbit. Planets clear their orbits of debris/asteroids (by attracting them with their gravity).

Pluto passes 1 and 2, but has not passed 3. It has not cleared it's orbit of debris.

Objects like Pluto are called Dwarf Planets.