Pluto and its moons

The distant dwarf planet will be examined in 2014 by the New Horizons spacecraft. Haim Mazar summarizes what is known so far about Pluto, Charon and the other two moons discovered in recent years

Pluto has an atmosphere 10,000 times thinner than Earth's, made mostly of nitrogen with small amounts of methane and carbon monoxide. During its orbit around the sun, during the winter season the atmosphere freezes slowly and falls to the ground. Observations from recent years have shown that it contains larger amounts of methane than previously estimated and that it is 40°C warmer than previously thought. Its temperature is 180°C and the ground temperature is 200°C. As you raise the atmosphere, it gets hotter. Every kilometer the temperature rises by 15-3°C. The explanation for this is in the layers or patches of methane on the ground that inhibit the evaporation of the nitrogen ice (1). Some of the changes observed on the ground with the Hubble telescope probably originate from basins and young craters, although most of the ground features discovered were probably created by the distribution of frost moving on the surface in parallel with the movement of Pluto around the sun and seasonal cycles. During the short warm period when Pluto approaches the sun the nitrogen ice, methane and carbon monoxide evaporate and enrich the atmosphere which is becoming denser. The light areas resemble Colorado snow. The dark areas are residual hydrocarbonaceous materials as a result of the sun's ultraviolet radiation and cosmic radiation (2). It turned out that with the warming of the atmosphere the temperature increases by 1.5°C and the density of the atmosphere doubles (3).

Between the years 2002-2003 the Hubble telescope made a series of photographs of Pluto. With the help of a special processing technique that lasted 4 years and involved 20 computers working simultaneously, extremely high-resolution photographs were obtained that made it possible for the first time to see the surface at an unprecedented level of detail, although it is still impossible to distinguish the craters if they do exist. It is possible to notice the seasonal changes that apply to the surface of the land. These changes are probably a product of the evaporation of the ice following the sun illuminating the surface. The sunlight causes the ice to evaporate at one pole and freeze it at the other pole. These new photographs testify to the complexity of the planet's soil. Their shades can be clearly distinguished - white, dark orange and jet black. It is the ultraviolet radiation of the sun that creates these colors. It decomposes the methane on the ground and leaves a carbon-rich residue on it.

When comparing these photographs with photographs taken in 1994 they clearly saw that the North Pole became brighter and the South Pole became darker. These differences indicate complex processes affecting the surface and that Pluto is a dynamic planet where dramatic atmospheric changes occur. The origin of these changes is the seasonal changes that are affected by Pluto's inclination and its eccentric orbit around the sun, in contrast to the Earth, which is only affected by its inclination. This route contributes to the fact that the seasons are not symmetrical in length. The transition from polar spring to summer is faster in the Northern Hemisphere because Pluto moves faster when its orbit is closer to the Sun. In these photographs, they also noticed a bright spot that was identified as particularly rich in carbon monoxide frost (4).

Charon

Charon is the largest moon of Pluto. Its diameter is 1200 km, it is 2,000 km away from it and circles it once in 6.6 days. Pluto also moves around itself once every 6.6 days and Charon only shows one side of it. They both show each other the same side. Charon in the form of its motion around Pluto is like a stationary equatorial satellite. The diameter of Pluto is 2200 km. This means that Pluto has a moon whose diameter is half that of its own. For comparison the diameter of our moon is ¼ that of the earth. The Pluto-Charon system can be thought of as a double planet. While the density of Pluto is 2 g/cm1.65, the density of Charon is 10 g/cm5 and its rocky mass is XNUMX% less than that of Pluto (XNUMX).

High-resolution spectral observations indicate that the moon emits ammonia hydrates and also ice crystals covering parts of its surface in a cryovolcanic process. It is believed that the origin of these is from the condensation of the earth. Inside the moon there is water in large quantities in a liquid state thanks to a radioactive heat source. They break out together with ammonia. It is the ammonia that maintains their liquid state of aggregation. The break out is through cracks and holes
The water outside rises up, freezes and returns to the ground in the form of ice. Since this process happens many times, there are probably layers of ice there. On the ground they look like bright spots. They can be seen in the near infrared. The ground temperature on the side not visible from Pluto is between -233-223C. (6)

Due to the close proximity between Pluto and Charon, strong mutual tidal forces can operate between them. It is possible that convection currents move within them at a depth of tens of kilometers. When they reach the same point that is in front of Charon or in front of Pluto, the tidal force of each of them acts on the other and creates a peak point, a kind of peak of a wave and as the flow continues, the peak point falls.

small moons

In recent years, two small moons have been discovered orbiting the Pluto-Charon system. One moon, named Nix, 88 km in size, orbits the system at a distance of 48,700 km once every 24.9 days. The second moon, Hydra, is 72 km in size and orbits the system at a distance of 64,800 km once every 38 days (7). These are probably lumps of rocks that lack a spherical shape, such as the asteroids and the small bodies that surround the gaseous planets. They appear to have been captured by the Pluto-Chron system and entered into orbit around it. If so, it is likely that other bodies were captured by the gravitational forces of Pluto and Charon and crushed their surfaces.
Sources

1."The lower atmosphere of Pluto revealed" 3.3. 2009
http://spacedaily.com/reports/ The_ Lower _Atmosphere_ Of_ Pluto_ Revealed_999.html

2."Pluto the full news release story"
http://hubblesite.org/newscenter/archive/releases/1996/09text/

3. "Does the atmosphere of Pluto go through the fast freeze?" 25.9.2006
http://spacedaily.com/reports/ Does _The_ Atmosphere_ Of_ Pluto_Goes_Through_ The _Fast_ Freese_999.html

4."Hubble catches Pluto changing with the year" 5.2.2010
http://spacedaily.com/reports/ Hubble_ Catches _Pluto _Changing_ With_ The_ Year_999.html

5. "Rare opportunity seized measure Pluto's large moon" 4.1.2006 http://www.spaceflightnow.com/news/n0601/04charon.

6."Charon: An ice machine in the ultimate deep freeze" 18.7.2007
http://spacedaily.com/reports/ Charon_An_ Ice_ Machine _In_ The_Ultimate_ Deep_ Freeze_999.html

7. Pluto
http://wikipedia.org?wiki/Pluto