Which of the following observations indicates that conditions on mars may have been suitable for life in the past? mars has two small moons. there are very large extinct volcanoes on mars. there are dried-up riverbeds on mars. there is a very deep and long canyon that extends across mars. mars has polar caps made of "dry ice."

There are dried-up riverbeds on Mars.

Explanation:

Now there is some evidence that is known that in Mars there is some water in layers below the soil, that mean that there are some possible storage of water. The life in Earth as we know it, it is possible just with the presence of water, that is the reason of this important knowledge.

In Mars atmosphere is almost carbon dioxide (aprox. 95 %) and just some traces of water, so the main source is located in soil.