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How does aqua regia dissolve gold and platinum?

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Viking 1 on Mars — sample preparation Viking 1's sample scoop, poised to extract material from the surface of Mars.

Aqua regia is a highly corrosive, fuming liquid mixture typically composed of one part concentrated nitric acid and three parts concentrated hydrochloric acid by volume.41

In the context of analytical chemistry, this mixture is an effective solvent for gold, platinum, and palladium. Its ability to dissolve these noble metals stems from the chemical synergy between its components: the nitric acid acts as a strong oxidizing agent, while the hydrochloric acid provides chloride ions that form stable, soluble complexes with the metal ions.123

Because it can dissolve materials that are otherwise highly resistant to acid, aqua regia is frequently used in sample preparation to bring inorganic samples, such as ores and alloys, into an acidic aqueous solution for further analysis. Due to its extreme corrosivity, it must be handled with significant caution to avoid skin burns and other hazards.41