Why does a dog ...

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Chirality: is the property of an object not being identical to its mirror image. An object is chiral if it is not identical to its mirror image; that is, it cannot be superposed (not to be confused with superimposed) onto it. Conversely, an object is achiral (sometimes also amphichiral) if its mirror image cannot be distinguished from the object (i.e. can be superposed onto its mirror image), such as a sphere. A chiral object and its mirror image are called enantiomorphs (Greek, "opposite forms") or, when referring to molecules, enantiomers. Chirality is a property of asymmetry important in several branches of science.

Two enantiomers of a generic amino acid that is chiral

Human hands are perhaps the most recognized example of chirality. The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide across all axes.[1] This difference in symmetry becomes obvious if someone attempts to shake the right hand of a person using their left hand, or if a left-handed glove is placed on a right hand. 

In the case of life, it's left handed, Why? Magnetism may be the answer. 

An RNA-making molecule crystallizes on magnetite,
which can bias the process toward a single chiral form.S. Furkan Ozturk

In 1848, French chemist Louis Pasteur discovered that some molecules essential for life exist in mirror image forms, much like our left and right hands. Today, we know biology chooses just one of these “chiral” forms: DNA, RNA, and their building blocks are all right-handed, whereas amino acids and proteins are all left-handed. Pasteur, who saw hints of this selectivity, or “homochirality,” thought magnetic fields might somehow explain it, but its origin has remained one of biology’s great mysteries. Now, it turns out Pasteur may have been onto something.

In three new papers, researchers suggest magnetic minerals common on early Earth could have caused key biomolecules to accumulate on their surface in just one mirror image form, setting off a positive feedback that continued to favor the same form. “It’s a real breakthrough,” says Jack Szostak, an origin of life chemist at the University of Chicago who was not involved with the new work. “Homochirality is essential to get biology started, and this is a possible—and I would say very likely—solution.”

Why all this quoted material, because Mirror Life is something else altogether.

To whit ...

In a mirror bacterium, all of the chiral molecules of existing bacteria—proteins, nucleic acids, and metabolites—are replaced by their mirror images. Mirror bacteria could not evolve from existing life, but their creation will become increasingly feasible as science advances. Interactions between organisms often depend on chirality, and so interactions between natural organisms and mirror bacteria would be profoundly different from those between natural organisms. Most importantly, immune defenses and predation typically rely on interactions between chiral molecules that could often fail to detect or kill mirror bacteria due to their reversed chirality. It therefore appears plausible, even likely, that sufficiently robust mirror bacteria could spread through the environment unchecked by natural biological controls and act as dangerous opportunistic pathogens in an unprecedentedly wide range of other multicellular organisms, including humans.

The argument ...

Scientists have warned that research into "mirror life" organisms — hypothetical life forms made up of molecules that perfectly mirror those found in regular life — should be stopped.

Theoretically, it's a cool idea. But some scientists are worried that these life forms, if they're ever realized, could turn into a major risk for the world around us by turning into an unstoppable force that spreads without limits, overrunning and choking out natural organisms in its path.

As Nature reported last year, mirror organisms could pose risks to pretty much all existing life if unleashed. They'd be like the ultimate invasive species, with no natural predators, and capable of evading pathogen detection systems found in nature because they're just so radically different.

In a 300-page technical report published by Stanford University in December, scientists laid out the risks posed by mirror life, from pandemics to crop losses and ecosystem collapse.

"The consequences could be globally disastrous," coauthor Jack Szostak, a Nobel-prize-winning chemist at the University of Chicago, told The New York Times at the time.

Other scientists, however, say these risks are completely overblown, as Nature noted in a follow-up article this week, pointing out we're likely still many years away from synthesizing larger mirror molecules, let alone entire organisms. And even if it did come to exist, and it did escape the lab, some experts think that nature would have ways to defend itself.

The disagreement has shaken the scientific community. This week, researchers convened in Manchester, UK, to debate whether research into mirror life should be allowed or halted.

Proponents of the research argue that "reverse chirality" molecules could be used to create promising new drugs, as they're not as readily recognized by the human body's enzymes and immune system. At the same time, such a resistance could be potentially dangerous, allowing drugs to proliferate uncontrollably in the body, according to Nature.

Biochemist and pharmaceutical founder Sven Klussmann told the publication that it's worth considering the risks.

"But we should not panic yet, and we should not restrict research too early," he said.

This is akin to Why does a dog lick its balls? Because it can. Think Edwin Teller and The Super.
Easier to produce than fission but Oppie opposed it. Guess who won. 

Ivy Mike, the first full test of the Teller–Ulam design (a staged fusion bomb),
with a yield of 10.4 megatons (November 1, 1952)

The real Dr. Strangelove

I first met Edward Teller, the Hungarian-born physicist and father of the H-bomb, while researching a television series about Robert Oppenheimer. Teller was seen as the embodiment of Dr Strangelove, the eponymous scientist in Stanley Kubrick's classic black comedy, and though he hated the association, it seemed appropriate enough.

In the luxurious house of a friend of Teller's in downtown Hollywood, the scriptwriter Peter Prince and I listened while Teller delivered an impassioned monologue justifying his actions over the Oppenheimer affair (of which more later). His words were given additional weight by his rich, Bela Lugosi baritone and we left feeling we had experienced something of the force of personality that had prevailed for 50 years over congressmen, generals and presidents. It was that meeting that drew me to write Teller's biography.

As well as "fathering" the H-bomb, it was at Livermore that Teller initiated the Polaris programme, which revolutionised nuclear strategy by producing warheads small enough to be launched from ever-elusive submarines. It was here also, during Eisenhower's presidency, that Teller generated a stream of technical objections why it would be impossible to maintain and monitor a test ban with an enemy as devious as the Soviets. In doing so he thwarted Eisenhower's dream of a test-ban to end the arms race. If Teller had trusted the Russians to negotiate the world may have been spared the trauma of the Cuban missile crisis.

Physicist Edward Teller was for many years the chief force
lobbying for research into developing fusion weapons

Whenever someone poo poos or supports something potentially really dangerous,

hubris or money is inevitably involved. 

And so it goes - K. Vonnegut