That's a bad idea. Ammonia ruins the screens on smartphones and tablets. Instead, remove the back case, battery and anything else you can take off. Then, use a micro-fiber cloth to wipe down the mobile gadget's screen. Don't use a paper towel, since these can knick the screen. If you've got stubborn streaks, you can dampen the cloth - not the screen - in some distilled water, or distilled water mixed with white vinegar or rubbing alcohol. A 1-1 ratio works best. You can use the same cloth or cotton swabs to clean the body of the smartphone, open ports and keyboard, if your phone or tablet has one.
Flying space rocks hit the Earth all the time. Most burn up in the atmosphere as shooting stars, but some make it to the ground - like the one that hit Russia on February 15.
There are many factors that go into how much damage a meteor can cause. If you want to calculate the damage that a rogue planet or meteor could do, visit Impact Earth.
You can select the diameter and density of your space rock, and then specify its trajectory and speed and velocity. Once you've created a meteor, click Calculate Impact to receive detailed information on the havoc it would cause.
You'll see the estimated global damages, the seismic and tsunami effects, the wind damage and details on the crater left behind. Not sure where to start? Load up the statistics from a famous meteor crater and go from there.