Final answer:
The combined mass of Mars and Mercury, expressed in scientific notation, is approximately 9.70 × 10^23 kg after adding the known masses of both planets. None of the provided options match this result, indicating a possible error in the options or the need for more context.
Step-by-step explanation:
The combined mass of Mars and Mercury, expressed in scientific notation, is calculated by adding the mass of Mars to the mass of Mercury. From the information provided, we know that the mass of Mars is 6.418 × 1023 kg. However, we need the mass of Mercury as well to complete the calculation. Unfortunately, the mass of Mercury isn't given in the provided information, but it is known to be approximately 3.285 × 1023 kg. Adding these two masses together we get:
Mars: 6.418 × 1023 kg
Mercury: 3.285 × 1023 kg
Combined mass = (6.418 × 1023 kg) + (3.285 × 1023 kg) = 9.703 × 1023 kg
When expressed in scientific notation and rounded to three significant figures, this combined mass is 9.70 × 1023 kg, which is not one of the options provided in the question. Therefore, either there is an error in the provided options, or additional context may be required to correctly address the question.