Lifeless, more like Mars
Earth's climates might be different because they won't be the same
Forget the atmosphere . . . if the magnetosphere went away, people would die horrible deaths and be largely gone in a couple of months. The magnetosphere helps carry damaging Solar particles to the south and north poles and then out into space. (Along with the Van Allen belt) If the atmosphere went away, people and animals would all die in about 10 minutes, except for SCUBA divers and firemen, who might last a quarter of a day.
The atmosphere can be classified based on its temperature profile into distinct layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. These layers vary in temperature, composition, and characteristics, with the troposphere being the layer closest to Earth's surface and the exosphere merging into outer space.
The Green House effect is important because there is a kind of gas that forms a "blanket" around Earth that holds heat in the atmosphere and keeps Earth's atmosphere at a temperature that is comfortable for most living things. So without it the temperature would go down to 50 degrees Fahrenheit (32 degrees Celsius) colder than it is. That would cause all water to freeze and the planet to turn into an ice cube. The earth would become a very large iceberg. The atmosphere would always be below freezing. All that ice reflects heat back into space so the earth would never warm up.
If Earth did not have any life, its atmosphere would likely consist mostly of nitrogen, similar to the atmosphere of Mars or Venus. Volcanic activity would have likely contributed to the release of gases like carbon dioxide and water vapor. Sunlight and cosmic rays might also have influenced the composition of the atmosphere over time.
If by gas you mean an atmosphere, there are no planets with an atmosphere anywhere similar to Earth.
It the earth was half its mass, then it might only be able to hold half the atmosphere. In this case, it may not be able to maintain many species of life as we know it.
The observation could be explained by the differences in wavelength or frequency between Waves A and B. Wave B might be absorbed or scattered by Earth's atmosphere due to its specific characteristics, while Wave A, with different properties, can pass through the atmosphere and into space without being affected in the same way.
There was a lot of methane.
Historians might need to describe different places on earth to add context to a historical situation. For example, the activities of the Mayan society might be interpreted differently without an accurate idea of the geographical aspects of the region.
Earth has an ozone layer in atmosphere. It is present in the stratospheric region. Other planets which have oxygen in their environment might have ozone.Some planets like earth do. Others might have.
The color depends on where, when, how and with what you are looking at the atmosphere. For example, astronaut might see it as "clear" but people watching a sunset might see it as more orange/red.
It has nothing to do with atmosphere. The earth and the asteroid are moving in roughly the same direction and the asteroid is not aimed at the center of the earth. Most asteroids will miss the earth, a few will pass close enough to enter the atmosphere then leave without hitting (some of these will explode before they can leave), others will hit at shallow angles.Perhaps one in a billion might hit near vertically.
Earth's climates might be different because they won't be the same
Forget the atmosphere . . . if the magnetosphere went away, people would die horrible deaths and be largely gone in a couple of months. The magnetosphere helps carry damaging Solar particles to the south and north poles and then out into space. (Along with the Van Allen belt) If the atmosphere went away, people and animals would all die in about 10 minutes, except for SCUBA divers and firemen, who might last a quarter of a day.
The atmosphere can be classified based on its temperature profile into distinct layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. These layers vary in temperature, composition, and characteristics, with the troposphere being the layer closest to Earth's surface and the exosphere merging into outer space.
You might mean nitrogen which is the colourless gas that constitutes about 3/4 of the earth's atmosphere.