cometary

just-some-writer  asked:

Imagine: an earth-like, inhabited planet slowly grows uninhabitable over hundreds of thousands of years and the atmpsphere no longer supports life. Would it be possible for that change to have made it easier for stuff to enter the atmosphere? To face less (but still some) resistance? I'm not really wanting to just straight-up weaken the atmosphere, but I need a space ship to crash on this planet and not burn up all the crew on entry while also being terraform-able. Thanks so much!

There are a couple of ways an atmosphere can change to make the planet less inhabitable for life-as-we-know-it.

1. The atmosphere can change it’s composition. For example, volcanic eruptions could kick enough bad stuff (sulfur dioxide and hydrogen sulfide can be very nasty) into the air. It would take a lot of volcanoes and quite a bit of time, but it’s plausible. Substitute regular asteroid or cometary impacts kicking up nasty stuff if you prefer that.

2. The atmosphere can get thinner.  For many reasons the planet’s atmosphere is getting thinner. This could be from an increase in solar activity or a weakening of the magnetic field around the planet allowing the solar wind to blow the atmosphere away. Maybe the gravity of the planet isn’t strong enough to hold an atmosphere for long and the air has been escaping to space for a long time (it’s been calculated that if we gave our Moon a breathable atmosphere, it would eventually escape into space after a couple of million years). This is the only way to make it easier to get to the surface from space.

However, it’s entirely plausible to have a spaceship built to encounter a mostly-uncontrolled reentry into a planets atmosphere and protect it’s crew. A civilization that can build real spaceships probable has the materials technology to make stuff that can survive a few minutes of very very high temperature of reentry.

Mind you, the ship might not be in any shape to re-fly, but that can lead to a great story about a scrappy bad of survivalists on a desolate planet.

Crashed spaceships surviving a crash onto planet are a staple of science fiction stories, and are completely plausible.

The Helix Nebula in Infrared : What makes this cosmic eye look so red? Dust. The featured image from the robotic Spitzer Space Telescope shows infrared light from the well-studied Helix Nebula a mere 700 light-years away in the constellation of the Water Carrier Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula, representing the final stages in the evolution of a Sun-like star. But the Spitzer data show the nebulas central star itself is immersed in a surprisingly bright infrared glow. Models suggest the glow is produced by a dust debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could have been generated by collisions in a reservoir of objects analogous to our own solar systems Kuiper Belt or cometary Oort cloud. Had the comet-like bodies formed in the distant planetary system, they would have survived even the dramatic late stages of the stars evolution. via NASA

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You think man can destroy the planet? What intoxicating vanity. Let me tell you about our planet. Earth is four-and-a-half-billion-years-old. There’s been life on it for nearly that long, 3.8 billion years. Bacteria first; later the first multicellular life, then the first complex creatures in the sea, on the land. Then finally the great sweeping ages of animals, the amphibians, the dinosaurs, at last the mammals, each one enduring millions on millions of years, great dynasties of creatures rising, flourishing, dying away – all this against a background of continuous and violent upheaval. Mountain ranges thrust up, eroded away, cometary impacts, volcano eruptions, oceans rising and falling, whole continents moving, an endless, constant, violent change, colliding, buckling to make mountains over millions of years. Earth has survived everything in its time. It will certainly survive us.
—  Ian Malcolm; Jurassic Park

“C/2014 Q2 Lovejoy”, by Michael Jaeger, Austria

“Comet Lovejoy sails through the solar system in a green haze leaving cometary dust in its wake. Towards the end of 2014 and into the beginning of 2015 the comet could be seen through binoculars or in some special cases with the naked eye soaring through Earth’s skies. The radiant blue-green contrasting against the backdrop of the night sky is due to the diatomic gas burning off it as it travels through space, and the disjointed tail illustrates the effects of a disturbance caused by solar winds.” – Astronomy Photographer of the Year 2015

Continued Mystery from Tabby’s Star

A year ago Tabby’s Star (officially known as KIC 8462852) made headlines when a scientific paper was published in arXiv detailing possible phenomena that could account for the strange dips in brightness around the star. The most reasonable explanation seems to be that a swarm of cometary debris surround the star and produce unusual drop-offs in its luminosity.

None of the presented arguments, however, could explain all the things we were seeing and so the scientific community naturally continued looking for explanations.

Eventually, as is typical in this field, we reached a point where many started considering the possibility of intelligent life.

For those not “in-the-know” a Dyson Sphere is a hypothetical structure (made of solar panels or some such things) surrounding a star which absorbs most of said star’s energy. It’s thought a feat of astro-engineering like this could be the powerhouse for a massive, advanced civilization.

Such an object, some argue, could replicate the strange behavior of Tabby’s star.

Now there’s been another paper published that pretty much furthers the mystery.

Trends in the stars brightness over a long term period can be explained, but only at the neglect of the short term trends and vice versa. It’s as if the star adopts a certain personality for awhile, then another for a much longer period of time and then another.

A technical look at what’s happening is this: the star has had occasional drops in luminosity ranging from 15-22% which would equal something roughly half the radius of the star blocking its light (that’s huge, imagine a planet half the size of the Sun). Furthermore, a look at photographs ranging back to when astronomers had to use photographic plates in the 1800′s show that the star has dropped in luminosity about 20% overall since then.

Long story short: we don’t have an answer to whatever strange thing is happening over there. The science continues and the Kepler spacecraft will next observe the star in May 2017. 

SETI Institute has conducted tests for radio signals from the region of KIC 8462852 and have thus far found no evidence for intelligent life.

(Image credit: IPAC/NASA and STScl/NASA)

“You think man can destroy the planet? What intoxicating vanity. Let me tell you about our planet. Earth is four-and-a-half-billion-years-old. There’s been life on it for nearly that long, 3.8 billion years. Bacteria first; later the first multicellular life, then the first complex creatures in the sea, on the land. Then finally the great sweeping ages of animals, the amphibians, the dinosaurs, at last the mammals, each one enduring millions on millions of years, great dynasties of creatures rising, flourishing, dying away – all this against a background of continuous and violent upheaval. Mountain ranges thrust up, eroded away, cometary impacts, volcano eruptions, oceans rising and falling, whole continents moving, an endless, constant, violent change, colliding, buckling to make mountains over millions of years. Earth has survived everything in its time. It will certainly survive us.

If all the nuclear weapons in the world went off at once and all the plants, all the animals died and the earth was sizzling hot for a hundred thousand years, life would survive, somewhere: under the soil, frozen in Arctic ice. Sooner or later, when the planet was no longer inhospitable, life would spread again. The evolutionary process would begin again. It might take a few billion years for life to regain its present variety. Of course, it would be very different from what it is now, but the earth would survive our folly, only we would not. If the ozone layer gets thinner, ultraviolet radiation sears the earth, so what? Ultraviolet radiation is good for life. It’s powerful energy. It promotes mutation, change. Many forms of life will thrive with more UV radiation. Many others will die out. Do you think this is the first time that’s happened?

Think about oxygen. Necessary for life now, but oxygen is actually a metabolic poison, a corrosive glass, like fluorine. When oxygen was first produced as a waste product by certain plant cells some three billion years ago, it created a crisis for all other life on earth. Those plants were polluting the environment, exhaling a lethal gas. Earth eventually had an atmosphere incompatible with life. Nevertheless, life on earth took care of itself. In the thinking of the human being a hundred years is a long time. A hundred years ago we didn’t have cars, airplanes, computers or vaccines. It was a whole different world, but to the earth, a hundred years is nothing. A million years is nothing. This planet lives and breathes on a much vaster scale. We can’t imagine its slow and powerful rhythms, and we haven’t got the humility to try. We’ve been residents here for the blink of an eye. If we’re gone tomorrow, the earth will not miss us.

 - Michael Crichton (author of Jurassic Park and Congo)

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As comets near the Sun, they start to change.

The light materials they’re made of, things like ammonia and water ice, start to undergo changes due to the heat of the Sun and the presence of the solar wind.

The Rosetta mission, currently in orbit around Comet 67P (and on 67P) have been taking close ups of the comet as it changes. You can see streamers beginning to form on the comet’s surface. Also of note is that there are several potential fractures appearing on the comet.

It will be exciting to watch 67P’s cometary tails form.

(Image credit: ESA)

An Unusual Globule in IC 1396 Energetic light from a bright young star is eating away the dust of the dark cometary globule near the top of the image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust

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Located roughly 1300 light years distant in the constellation Pupis at the southern end of the great Gum Nebula; these objects are what are known as cometary globule complex CG30, CG31 & CG38.

Created by gravity; these pockets of dense interstellar gas and dust stretch roughly one light year and are molded into their comet-like shapes through ionization by nearby stars that shower them with energetic ultraviolet (UV) radiation.

In the dense heads of these universal sculptures lie infant stars that are still undergoing formation. Over time gravity will continue to pool material into the densest regions. It will then contract, collapse and heat the local region.

This process will repeat over and over until it reaches the critical point where the conditions allow for fusion to take place and the star will come to life.

In the annotated image presented below.  The head of CG30 contains the bright Herbig-Haro object HH120 that is powered by a young star, CG 30-IRS4 based upon IR data.   Distance estimates are 700-1300 light years.  The image is ~42’ x 42’ and North is down.

CG30,31 is a cometary globule complex located in southern portion of the large Gum Nebula at RA 8hr 08min 50.5s and DEC -35d 50m 54s near the constellations of Vela and Pupis.

Overall, we think the Gum Nebula is pretty cool! Well actually it is fascinating in our books…

Re-blog & follow if you agree and want to see more amazing space pictures, facts and news!

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Check out these amazing new images of Comet 67P/Churyumov-Gerasimenko by the ESA’s Rosetta spacecraft.

The top row are images edited to enhance the view of the new streamers flying from the comet as it approaches the Sun.

The bottom show the comet’s images as taken by Rosetta’s NAVCAM.

As Comet 67P gets closer to the Sun, it’s going to continue putting on a crazy light show that’s only going to get more wild. Heat from the Sun will turn much of the ice on 67P into a hazy atmosphere called a ‘coma’ and the solar wind will ionize lots of the gas on the comet as well as blow the dust out, eventually both will become prominent cometary tails.

By the way, this weekend on February 14th the Rosetta spacecraft is going to do an up-close flyby of 67P’s surface. The images are going to be remarkable.

(Image credit: ESA)