Space and astronomy news
Uranus is an oddball among the Solar System’s planets. While most planets’ axis of rotation is perpendicular to their orbital plane, Uranus has an extreme tilt angle of 98 degrees. It’s flopped over on its side, likely from an ancient collision. It also has a retrograde orbit, opposite of the other planets.
The ice giant also has an unusual relationship with the Sun that sets it apart from other planets.
Continue reading “Uranus is Getting Colder and Now We Know Why”
The theory of Panspermia states that life exists through the cosmos, and is distributed between planets, stars and even galaxies by asteroids, comets, meteors and planetoids. In this respect, life began on Earth about 4 billion years ago after microorganisms hitching a ride on space rocks landed on the surface. Over the years, considerable research has been devoted towards demonstrating that the various aspects of this theory work.
The latest comes from the University of Edinburgh, where Professor Arjun Berera offers another possible method for the transport of life-bearing molecules. According to his recent study, space dust that periodically comes into contact with Earth’s atmosphere could be what brought life to our world billions of years ago. If true, this same mechanism could be responsible for the distribution of life throughout the Universe.
For the sake of his study, which was recently published in Astrobiology under the title “Space Dust Collisions as a Planetary Escape Mechanism“, Prof. Berera examined the possibility that space dust could facilitate the escape of particles from Earth’s atmosphere. These include molecules that indicate the presence of life on Earth (aka. biosignatures), but also microbial life and molecules that are essential to life.
Fast-moving flows of interplanetary dust impact our atmosphere on a regular basis, at a rate of about 100,000 kg (110 tons) a day. This dust ranges in mass from 10-18 to 1 gram, and can reach speeds of 10 to 70 km/s (6.21 to 43.49 mps). As a result, this dust is capable of impacting Earth with enough energy to knock molecules out of the atmosphere and into space.
These molecules would consist largely of those that are present in the thermosphere. At this level, those particles would consist largely of chemically disassociated elements, such as molecular nitrogen and oxygen. But even at this high altitude, larger particles – such as those that are capable of harboring bacteria or organic molecules – have also been known to exist. As Dr. Berera states in his study:
“For particles that form the thermosphere or above or reach there from the ground, if they collide with this space dust, they can be displaced, altered in form or carried off by incoming space dust. This may have consequences for weather and wind, but most intriguing and the focus of this paper, is the possibility that such collisions can give particles in the atmosphere the necessary escape velocity and upward trajectory to escape Earth’s gravity.”
Of course, the process of molecules escaping our atmosphere presents certain difficulties. For starters, it requires that there be enough upward force that can accelerate these particles to escape velocity speeds. Second, if these particle are accelerated from too low an altitude (i.e. in the stratosphere or below), the atmospheric density will be high enough to create drag forces that will slow the upward-moving particles.
In addition, as a result of their fast upward travel, these particle would undergo immense heating to the point of evaporation. So while wind, lighting, volcanoes, etc. would be capable of imparting huge forces at lower altitudes, they would not be able to accelerate intact particles to the point where they could achieve escape velocity. On the other hand, in the upper part of the mesosphere and thermosphere, particles would not suffer much drag or heating.
As such, Berera concludes that only atoms and molecules that are already found in the higher atmosphere could be propelled into space by space dust collisions. The mechanism for propelling them there would likely consist of a double state approach, whereby they are first hurled into the lower thermosphere or higher by some mechanism and then propelled even harder by fast space dust collision.
After calculating the speed at which space dust impacts our atmosphere, Berera determined that molecules that exist at an altitude of 150 km (93 mi) or higher above Earth’s surface would be knocked beyond the limit of Earth’s gravity. These molecules would then be in near-Earth space, where they could be picked up by passing objects such as comets, asteroid or other Near-Earth Objects (NEO) and carried to other planets.
Naturally, this raises another all-important question, which is whether or not these organisms could survive in space. But as Berera notes, previous studies have borne out the ability of microbes to survive in space:
“Should some microbial particles manage the perilous journey upward and out of the Earth’s gravity, the question remains how well they will survive in the harsh environment of space. Bacterial spores have been left on the exterior of the International Space Station at altitude ~400km, in a near vacuum environment of space, where there is nearly no water, considerable radiation, and with temperatures ranging from 332K on the sun side to 252K on the shadow side, and have survived 1.5 years.”
Another thing Berera considers is the strange case of tardigrades, the eight-legged micro-animals that are also known as “water bears”. Previous experiments have shown that this species is capable of surviving in space, being both strongly resistant to radiation and desiccation. So it is possible that such organisms, if they were knocked out of Earth’s upper atmosphere, could survive long enough to hitch a ride to another planet
“The proposition that space dust collisions could propel organisms over enormous distances between planets raises some exciting prospects of how life and the atmospheres of planets originated. The streaming of fast space dust is found throughout planetary systems and could be a common factor in proliferating life.”
In addition to offering a fresh take on Panspermia, Berera’s study is also significant when it comes to the study of how life evolved on Earth. If biological molecules and bacteria have been escaping Earth’s atmosphere continuously over the course of its existence, then this would suggest that it could still be floating out in the Solar System, possibly within comets and asteroids.
These biological samples, if they could be accessed and studied, would serve as a timeline for the evolution of microbial life on Earth. It’s also possible that Earth-borne bacteria survive today on other planets, possibly on Mars or other bodies where they locked away in permafrost or ice. These colonies would basically be time capsules, containing preserved life that could date back billions of years.
Further Reading: University of Edinburgh, Astrobiology
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Seen from space, the Earth’s atmosphere is incredibly thin, like a slight haze around the planet. But the atmosphere has several different layers that scientists have identified; from the thick atmosphere that we breathe to the tenuous exosphere that extends out thousands of kilometers from the Earth. Let’s take a look at the different atmosphere layers.
Scientists have identified 5 distinct layers of the atmosphere, starting with the thickest near the surface, and then thinning out until it eventually merges with space.
The troposphere is the first layer above the surface of the Earth, and it contains 75% of the Earth’s atmosphere, and 99% of its water. Breathe in, that’s the troposphere. The average depth of the troposphere is about 17 km high. It gets deeper in the tropical regions, up to 20 km, and then shallower near the Earth’s poles – down to 7 km thick. Temperature and pressure are at the their highest at sea level, and then decrease with altitude. The troposphere is also where we experience weather.
The next atmosphere layer is the stratosphere, extending above the troposphere to an altitude of 51 km. Unlike the troposphere, temperature actually increases with height. Commercial airlines will typically fly in the stratosphere because it’s very stable; above weather, and allows them to optimize burning jet fuel. You might be surprised to know that bacterial life survives in the stratosphere.
Above that is the mesosphere, which starts at about 50-85 km above the Earth’s surface and extends up to an altitude of 80-90 km. Temperatures decrease the higher you go in the mesosphere, reaching a low of -100 °C, depending on the latitude and season.
Next comes the thermosphere. This region starts around 90 km above the Earth and goes up to about 320 and 380 km. The International Space Station orbits within the thermosphere. This is the region of the atmosphere where ultraviolet radiation causes ionization, and we can see auroras. Temperatures in the thermosphere can actually reach 2,500 °C; however, it wouldn’t feel warm because the atmosphere is so thin.
The 5th and final layer of the Earth’s atmosphere is the exosphere. This starts above the thermosphere and extends out for hundreds and even thousands of kilometers. Air molecules in this region can travel for hundreds of kilometers without bouncing into another particle.
We have written many articles about the Earth’s atmosphere for Universe Today. Here’s an article about the composition of the Earth’s atmosphere, and here’s information about the Earth’s early atmosphere.
Here’s a great article from NASA that explains the different layers of the atmosphere, and here’s more information from NOAA.
We have done a whole episode of Astronomy Cast just about Earth. Listen to it here, Episode 51 – Earth.