Reducing in this context means decreasing in amount or intensity.

[RJ Emery]

What is the difference between salty and saline?

And in the context below, what is meant by reducing?

Consider the following excerpt:

Yet the largest question of all remains unanswered -- did Mars once harbor life? At the present time, the evidence seems stacked against it, for both [Spirit's and Opportunity's] data suggest that the surface of Mars is, and perhaps always was, oxygenating, acidic, and saline. Compare this situation with that on Earth at the time life got started. The atmosphere here then was reducing and with a neutral pH. The oceans were salty rather than saline.

Today's Earth does host extraordinary single-celled organisms that can live in very acidic environments -- the so-called acidiphiles. But, although they can live in concentrated sulphuric acid with a pH of 1, inside the cell the pH is a neutral 7, just as it was when their remotest ancestors evolved in the primordial sea of Earth. Acidiphiles have evolved sophisticated ion pumps across their cell membranes that protect them from the unbelievable harshness of their environment. Could they have originally evolved in such acidity? Probably not.

(end quote)

From Lives of the Planets: A Natural History of the Solar System, by Richard Corfield, 2007, Basic Books, ISBN 0465014038, Chapter 5, The Martian Chronicles - Mars, pp. 132-133.

 

[lisab]

If I remember correctly, saline refers to a salt of sodium, potassium, or magnesium. "Salty," in this context, would refer to NaCl.

The term "reduce" means an atom or molecule gains an electron. The text describes the Mars surface as "oxygenating," a term used to describe a molecule or atom that loses an electron.

 

[binzing]

I agree with lisa, and in scientific terms you don't say "salty" it sounds kinda stupid.