Discovered by Geoffrey Marcy and R. Paul Butler in 2004, this oxymoron of a title refers to the planet Gliese 436 b.
Gliese 436 b is known as one of the smallest exoplanets (planets that exist outside of the solar system), very close to the radius and mass of Neptune. But even more interesting than its size relative to other exoplanets, is its distance from its sun.
Gliese 436 is a red dwarf star less luminous than ours, and is close enough to our solar system that it can be viewed in the zodiac constellation Leo. Gliese 436 b is only 2.5 million miles away from Gliese 436. For comparison, Mercury (the closest planet to the sun in our solar system) is nearly 36 million miles from the sun. The planet completes a whole revolution in only 2 days and 15.5 hours, and its surface temperature is around 439 degrees Celsius (for reference, the boiling point of water is 100 degrees Celsius).
But if the surface temperature is so much higher than the boiling point of water, how is there ice? Let alone, how can ice burn?
Scientists and astronomers have concluded that the form of ice that exists on Gliese 436 b is held in solid state due to the incredible gravitational force pulling from the planet’s core. The gravitational force increases with depth, and prevents the water from evaporating the way it does on Earth. For reference, there are many different states of water that we have not seen on Earth, because only three forms can exist in our environment. The water on Gliese 436 b is subject to an environment that makes the ice much denser than what we see here, and it is hypothesized as Ice VII, a cubic, crystalline form that has been manufactured in labs.
Similar to how when carbon turns into diamonds when exposed to immense heat and pressure, when the water on Gliese 436 b was exposed to the same conditions, it turns into “burning ice”.
Gliese 436 b defies every norm we would assume about a planet from a scientific perspective. Not only does it contain the hottest ice in the known universe, but being composed primarily of hydrogen not just on the surface but in its atmosphere, our exofriend should have significant levels of methane. However, it has 7,000 times less than it should, and a significant amount of carbon monoxide instead. Which is especially weird because carbon monoxide molecules should not be present to this degree, as it becomes scarce when temperatures exceed a certain threshold.
Yay for flaming ice poison air planet!
Furthermore, the planet (or its atmosphere) is evaporating. In a strange way, however. Gliese 436 b has a massive hydrogen cloud surrounding the planet that is suspected to be the result of immense pressure exerted by its proximity to Gliese 436. Scientists suspect that the planet has lost up to 10% of its atmosphere already, which they have analyzed through the ultraviolet eye of the Hubble telescope, as the cloud cannot be seen in visible wavelengths of light. The cloud itself is about 50 times the size of the parent star, and it does not get swept away by solar winds from Gliese 436 or is burned up because Gliese 436 is much cooler than normal stars. Similar to the tail of a comet, the hydrogen cloud follows Gliese 436 b along its orbit, and actually obscures the view of the planet from scientists, making it ever more difficult to learn more about this supposed scientific impossibility.