Horizontal rains

This time I am blogging on a topic of general interest to many people; planets which can allow horizontal rains to occur and the implications of its occurrence for life on those planets. Horizontal rains are strictly not rains since they do not touch the ground; they travel parallel to the surface of the planet. When someone says that the rain is horizontal, it means that the distance between the center of gravity of the rain droplet and the point on the surface at intersection of the line segment joining the center of gravity of the rain droplet and the center of gravity of the planet with the solid surface of the planet is constant.

I believe that there are at least two scenarios which we will broach here where such rain is possible.

1) The rain could exist if it occurs with a certain velocity and at a distance from the center of the planet where it is in free fall like the geostationary satellites which orbit the earth. One way the rain could form at that height is through a collision of the planet with a large space object reducing the planet's size and leaving the rain in orbit. It could also form when the atmosphere of the planet is denser than the rain leading to a situation where the rain is pushed to the height of the geosynchronous orbit. The velocity in this case could to be acquired from collisions which happened in the past or as a result of the ionization of liquid particles in the strong magnetic field of the star and the star's changing magnetic field creating an electric field which drives the ionized rain.

2) The rain could also occur when the liquid on the surface of the planet is a superfluid. (Superfluids have no viscosity, hence can flow endlessly). The necessary condition here is that the superfluid has to be trapped in its heavy atmosphere allowing it to flow endlessly and close to its surface. The atmosphere should take the form of the surface upon which it rests allowing the rain to flow in it while maintaining a constant distance from the surface. The reason we need a heavy atmosphere in this case is because it needs to be of uniform thickness and accurately mimic the planet's solid surface.

There are a few other scenarios which we have not explicitly considered here. For example, one with extremely low density liquids floating above the gaseous atmosphere; or extremely small and low density planets having their geosynchronous orbit very close to their surface. These can be considered to be special cases of the first two scenarios which were mentioned earlier. It is important to note here that gaseous planets with small sizes do not fit the bill of small low density planers because the low mass makes them inherently unstable. So, the small low density planets mentioned above should have a solid surface made of low density materials (think aerogels).

The implications for life of having a horizontal rain on their planet depends on the specific scenario in which this is occuring. In the case of the rain circling the planet in the geosynchronous orbit, the life on the planet would have to be based not on the liquid that circles them, but on something else. Alternatively it could gain energy from the electric field generated by the ionized rain. Note that no magnetic field is created on the planet's surface in this case because the ionized particles in the rain are stationary with respect to the surface.

The implications in case of a superfluid rain are more difficult to ascertain as uncertainty exists regarding the existence of life in an environment where the liquid in the body does not have viscosity. If the liquid of the rain is different from the primary liquid needed for life on the planet, then one implication is that life there should not show toxicity for the rain. This is necessitated by the ability of the superfluid rain to enter the body through the pores. Alternatively, the life on the planet could be completely solid requiring no pores; indicating a lack of need for metabolism. The existence of life without need for liquids and metabolism is not impossible considering that many of the man-made objects which mimic life have neither liquids nor pores and a general definition of life is yet to be agreed upon.

As a closing note it is important to note what the blog post leaves out. It does not question the laws of physics; and it does not explore in detail the various ways in which life can exist. Horizontal rains and implications for aquatic life is another omission which could turn out to be extremely interesting.