[lokumologist (OP)]

I wonder how can we detect organic compounds with polarized light using chirality.I mean,only organic compound can be optically active if I don't know wrong and it can be used on rovers that are went to mars but how could we create a system for this if we would like to send a rover to mars ?

[Bored chemist]

only organic compound can be optically active if I don't know wrong

You are mistaken.
Plenty of inorganic things are optically active - notably quartz which is very common.

[chiralSPO]

Some of the issues here might just be based on nomenclature.
chiral describes molecules that are not superimposable on their mirror images (capable of rotating plane-polarized light)
achiral describes molecules that are superimposable on their mirror images (INCAPABLE of rotating plane-polarized light)
enantiomers are the two non-superimposable mirror images (they come in pairs) (each rotates plane-polarized light the opposite direction and same magnitude as the other)
enantiopure describes a sample containing only one of the two possible enantiomers (will rotate plane-polarized light)
scalemic describes an unequal mixture of enantiomers (will rotate plane-polarized light)
racemic describes an equal mixture of enantiomers (will NOT rotate plane-polarized light because each enantiomer undoes what the other one does)

There are plenty of chiral compounds that are not organic (like quartz, as Bored chemist pointed out). Individual quartz crystals will have one orientation or another, but it is (nearly) completely random: a single crystal is scalemic (or even enantiopure), but we expect a large collection of crystals to be racemic. So, if your sample is large enough and randomly sourced enough, it will not rotate plane-polarized light.

There are also plenty of organic (biologically derived) compounds that are achiral or racemic mixtures, and also will not contribute to optical rotation.

Another problem with this approach is that even if there are multiple scalemic compounds, they might rotate light in opposite ways anyway, and effectively cancel out (you'd have to be very unfortunate for it to exactly cancel, but I wouldn't design it in either).

[evan_au]

if there are multiple scalemic compounds, they might rotate light in opposite ways

This cancellation happens with biological molecules on Earth:

most amino acids are levorotatory (l) and sugars are dextrorotatory (d).

...so they tend to cancel each other, to some extent.
See: https://en.wikipedia.org/wiki/Chirality_(chemistry)#In_biochemistry

PS: Determinative Nominism, @chiralSPO

[chiralSPO]

PS: Determinative Nominism, @chiralSPO

In this case, the occupation predates the name.

[Colin2B]

In this case, the occupation predates the name.

I did wonder if that was why you chose it, but I couldn’t work out the SPO bit, unless they are your initials?

[chiralSPO]

In this case, the occupation predates the name.

I did wonder if that was why you chose it, but I couldn’t work out the SPO bit, unless they are your initials?

Nope, not my initials. If I google "chiral SPO" the 1st page of results contains the answer repeatedly, no need to even click the links. Of course, my cookies also predispose these kinds of results to pop up, so I don't know what you will find.

[lokumologist (OP)]

Okey then.How can we eliminate these risks that you told.

[chiralSPO]

Okey then.How can we eliminate these risks that you told.

Rather than looking for the extent to which a single wavelength is rotated, looking across a spectrum, or at least a number of frequencies, will be much more informative, and would avoid some sources of type I error , and some sources of type II error. This kind of test is often referred to as circular dichroism spectroscopy. https://en.wikipedia.org/wiki/Circular_dichroism

However, this technique still won't be particularly helpful when trying to determine "what" the scalemic sample is, even if one can more accurately identify that a sample is scalmeic. Even with reference CD spectra, a mixture of more than a few chiral species could be incredibly difficult to deconvolute.

There is no guarantee that exobiotic organisms would leave a chiral trace, or that detection of a highly enantioenriched sample is indicative of life, without knowing "what" the chiral stuff is.