Hey guys, Amy here with DNews. We haven’t found extraterrestrial life just yet, but

that might be because we’re looking for entirely the wrong thing.

Let’s start with a recap of life as we know it on Earth. Carbon, hydrogen, nitrogen, oxygen,

phosphorus and sulfur are the six basic building blocks of all life forms on Earth, at least

that we know of. Phosphorus is an integral part of DNA and RNA, the structures that carry

all the genetic instructions for life. Carbon, meanwhile, is the main component of sugars,

proteins, fats, DNA, muscle tissue… pretty much everything that makes up your body. Life

on Earth also requires something called a phospholipid bilayer membrane, a strong, permeable,

water-based membrane that houses the organic matter inside every cell, vesicles made of

which are called liposomes.

So these are the things astronomers look for on other planets and in alien environments

to find life. And because all life on Earth needs water, we tend to look for water in

the search for extraterrestrial life.

But there’s increasingly more research to suggest that life on other worlds won’t

necessarily have the same makeup as life does here.

In 2010, a team of researchers released a study saying they’d discovered the first

known microorganism able to thrive and reproduce using arsenic, a toxic chemical. In a laboratory

setting, researchers successfully grew a strain of Gammaproteobacteria microorganisms on a

diet lean on phosphorus and heavy on arsenic before removing the phosphorous entirely.

The microbes didn’t die. Instead, they thrived, with later generations substituting arsenic

for phosphorus in its DNA and other cellular components. The arsenic became a building

block for a new strain of cells.

When this news came out it was massively exciting for the astrobiology and space world, but

the discovery was eventually debunked. The phosphate-free medium in which the microbes

thrived with arsenic in their DNA turned out to have just enough phosphate in it to support

life as we know it.

But it didn’t turn out to be the nail in the coffin of finding interesting alien life.

Just last month, scientists at Cornell University modeled a cell that could exist on Saturn’s

moon Titan. Titan, Saturn’s largest moon, has a thick atmosphere, liquid ethane and

methane seas, and organic-rich chemistry somewhat reminiscent of a frozen early Earth. Titan

couldn’t support organic cells as they exist on Earth, but it could support methane-based,

oxygen-free cells.

The researchers theorized a cell membrane called an “azotosome.” It’s a membrane

analogous to the liposomes we know exist in Earthly life; it has the same stability and

flexibility. But these azotosomes are made from nitrogen, carbon and hydrogen molecules,

molecules we know exist in Titan’s seas. So it’s possible that carbon-free life could

exist on Titan, or else on some exoplanet or exomoon with a similar structure.

So, to be fair, the arsenic-based bacteria was eventually disproved and the possible

cell that could exist on Titan is only a model. But still, the definition of life keeps expanding

and that makes the ongoing search for extraterrestrial life that much more interesting.

And switching gears just a little, we are really happy that our new channel Seeker launched

this week! Here on DNews, we take a look at the news from a science angle, and they take

a look at the news from a human side! Like this video here about the fight to save New

York subway dancers...

So make sure you check that video out, it’s the first link in the description, and subscribe

to Seeker so you never miss a video!

So what do you guys think about non carbon-based life forms? Cool science fact or unlikely

science fiction? Let us know in the comments below or you can

let me know directly on Twitter as @astVintageSpace. And don’t forget to subscribe for more DNews

every day of the week.