Earth changes?

The phrase "earth changes" is often used to refer to some kind of disastrous event that will adversely affect much if not most life on Earth, including human life. There is thought about preparing ourselves for it, but the phrase is vague about what it could be.

CMEs, SPEs

Among the kinds of CMEs that can severely threaten much of the life on Earth are the coronal proton ejections (CPE) or Solar Proton Events (SPEs)  that have have appeared to have occurred several times in history. One such event today could wipe out much of humanity and leave the Earth devastated. It could bring radiation, massive wildfires, and other destructive events.

It differs in severity from coronal mass ejections like the Carrington event of 1859, Those are CMEs, but do not in general threaten life rather than power grids, which could be devastating enough in this modern age of dependence on electronic devices of all kinds. There are calls such as the Shield Act to harden electric grids against them.

The main suspected SPE impacted the earth about 12,900 years ago. There may have two such events, 12,837 years BP and 12,639 years BP. They could have been a principal cause of the final termination of the Pleistocene megafauna and even of several genera of smaller mammals and birds. There is also evidence of less intense event in 2012 that missed the Earth by only two weeks. One of the things that it does that could cause mass extinctions is to raise the level of proton bombardment to fatal levels. They are also suspected of causing massive, planet spanning wildfires.

Type G stars like the sun are not observed to produce massive flares such as the one hypothesized to have harmed life on Earth. The only stars observed to do that are type "T Tauri" stars, but those stars are young, only about 100 million years old. They are generally composed of almost pure hydrogen, with little helium or traces of heavier elements. They are typically surrounded by rings of debris, thought to be primordial planets. The sun is about 4.6 billion years old. It contains helium and other heavy elements. T Tauri stars flare frequently and massively. But it seems unlikely that the sun would revert to a T Tauri phase.

There does not appear to be evidence of previous proton storms that could have caused mass extinctions. The 12,900 year old labrean
(named after the tar pits that captured so many of the species that went extinct) extinction appears to have been a rare event.

A mistake made by some investigators is to call the solar protons "cosmic rays", which are also mostly protons, but much more energetic and moving at nearly the speed of light. Solar protons are produced steadily, and largely comprise the "solar wind" that can damage equipment and deliver near-lethal doses of radiation to astronauts. But flares of solar protons can be detected while they are still hours away, and astronauts can take enough cover in compartments shielded by fuel and supplies. Such shielding is not enough for cosmic rays.

This is why planned colonies on Mars are going to need to build underground, to shield colonists from radiation.

Grazing rogue planets

There are interstellar objects that might make a grazing contact with the sun, We recently had one such object, Oumuamua, an odd-shaped body about ten times longer than it was wide, with other strange attributes. The general name for interstellar planets, not bound to a particular star, is rogue planet. Most of them are expected to be round. They could be as large as Jupiter. The term usually applies to a rocky object, perhaps with a hot core, that could wander among the stars, and could provide a site for an outpost for star travelers, if the core is hot enough to geothermally support such an outpost. Grazing the sun could produce a proton flare large enough to become a mass extinction event.

A rogue planet with enough of an infrared signature could be detected when it it still 100 billion miles from the sun, if we were looking for it. If it were moving at the speed of the fastest known star, 26 million miles an hour, it would close on the sun in about 4000 hours, or about 6 months. That would be enough time to find or build shelters for much of the human population, but not enough to protect most wildlife. 

Notes:
  1. Did A Massive Solar Proton Event Fry The Earth?
  2. Solar flare nearly destroyed Earth 2 years ago: NASA
  3. Coronal mass ejection — An event like the 1859 Carrington event could disrupt power grids.
  4. Shield Act — Would protect power grids from coronal mass ejections, and from EMP attacks, but not the rest of the electronic infrastructure on which our economy depends.
  5. Rogue planet — Planetary body not gravitationally bound to a star.
  6. Oumuamua — Odd-shaped interstellar object flys through solar system.
  7. Fastest Star in the Galaxy Has a Strange Origin — Moves about 26 million miles an hour. 
  8. Mars Colonists Could Live in Lava Tubes Beneath the Surface  — Could fit entire cities into such tubes.
  9. Living Underground on Other Worlds  — We can see skylights of partially collapsed tubes.
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