Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury .
In English, Mars carries a name of the Roman god of war , and is often referred to as the “Red Planet“ because the iron oxide prevalent on its surface gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye.
Mars is a terrestrial planet with a thin atmosphere , having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth .
Like Earth, Mars has differentiated into a dense metallic core overlaid by less dense materials.
This iron(II) sulfide core is thought to be twice as rich in lighter elements as Earth’s.
The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet.
Elements in the Martian crust are iron, magnesium , aluminum , calcium , and potassium .
The average thickness of the planet’s crust is about 50 km (31 mi).
Earth’s crust averages 40 km (25 mi).
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A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth’s atmosphere at extremely high speeds on parallel trajectories.
Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit the Earth’s surface. Very intense or unusual meteor showers are known as meteor outbursts and meteor storms, which produce at least 1,000 meteors an hour, most notably from the Leonids.
The Meteor Data Centre lists over 900 suspected meteor showers of which about 100 are well established. Several organizations point to viewing opportunities on the Internet.
The first great meteor storm in the modern era was the Leonids of November 1833. One estimate is a peak rate of over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of two hundred thousand meteors during the 9 hours of storm, over the entire region of North America east of the Rocky Mountains.
American Denison Olmsted (1791–1859) explained the event most accurately. After spending the last weeks of 1833 collecting information, he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836.
He noted the shower was of short duration and was not seen in Europe, and that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space.
Work continued, yet coming to understand the annual nature of showers though the occurrences of storms perplexed researchers.
Famous meteor showers:
Perseids and Leonids
Other meteor showers
Established meteor showers
Extraterrestrial meteor showers
Any other solar system body with a reasonably transparent atmosphere can also have meteor showers. As the Moon is in the neighborhood of Earth it can experience the same showers, but will have its own phenomena due to its lack of an atmosphere per se, such as vastly increasing its sodium tail.
NASA now maintains an ongoing database of observed impacts on the moon maintained by the Marshall Space Flight Center whether from a shower or not.
Many planets and moons have impact craters dating back large spans of time. But new craters, perhaps even related to meteor showers are possible. Mars, and thus its moons, is known to have meteor showers.
These have not been observed on other planets as yet but may be presumed to exist. For Mars in particular, although these are different from the ones seen on Earth because the different orbits of Mars and Earth relative to the orbits of comets.
The Martian atmosphere has less than one percent of the density of Earth’s at ground level, at their upper edges, where meteoroids strike, the two are more similar.
Because of the similar air pressure at altitudes for meteors, the effects are much the same.
Only the relatively slower motion of the meteoroids due to increased distance from the sun should marginally decrease meteor brightness. This is somewhat balanced in that the slower descent means that Martian meteors have more time in which to ablate.
The moon has always served as an inspiration for humanity, and there are many potential benefits for further exploration of our planet’s rocky satellite.
But we need to establish guidelines to prevent unethical behavior on the moon, particularly regarding the use of natural resources and off-planet labor.
How humans should interact with space and celestial objects is central to the emerging field of space ethics. It’s something I’ve been involved with since 2015, when I taught my first class on consent for the use of celestial objects at Yale University’s Summer Bioethics Institute.
1. Human settlement on the moon
Some people believe establishing human settlements on the moon — and other bodies — may help lessen the environmental burden of overpopulation on Earth.
While the practical issues of survival and maintaining communication receive a lot of attention in discussions of moon settlements, the ethical considerations are often overlooked.
As with all mining projects on Earth, there are concerns about environmental sustainability and whether it is appropriate for mining corporations to profit from the commercialisation of natural resources in space.
3D printing organs on the moon, where gravity is one-sixth that on Earth, could be the next step in addressing the shortage of organs available for transplant. Then there’s the possibility of other medical research on the moon.
There are strict regulations for medical research in most countries on Earth, and experiments on the ISS are done under the watch of the station’s partners. But there is no global system in place to review whether proposed medical studies on the moon are ethically acceptable.
Over the eight-day, 3-hour Apollo 11 mission, astronauts Neil Armstrong, Buzz Aldrin and Michael Collins stayed in constant communication with mission control and supporting teams. The back-and-forth conversations, which took place over what are called communication “loops,” were released to the media, because NASA is required to make its work public. But these fragile physical recordings had to be stored in special, climate-controlled vaults.
The Milky Way is the galaxy that contains the Solar System. The name describes the galaxy’s appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος (galaxías kýklos, “milky circle”).From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610.
Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe.Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.