Martian soil perchlorate readings being caused by terrestrial sources, which at the time were thought could have migrated from the spacecraft either into samples or the instrumentation. However, each new lander has confirmed their presence in the soil locally and the "Mars Odyssey" orbiter confirmed they are spread globally across the entire surface of the planet. While our understanding of Martian soils is extremely rudimentary, their diversity may raise the question of how we might compare them with our Earth-based soils. Applying an Earth-based system is largely debatable but a simple option is to distinguish the (largely) biotic Earth from the abiotic
Solar conjunction the line of sight to an interior planet (Mercury or Venus) being very close to the solar disk. If the planet passes directly in front of the sun, a solar transit occurs. Solar conjunction Solar conjunction occurs when a planet or other solar system object is on the opposite side of the sun from the Earth. From an Earth reference, the sun will pass between the Earth and the object. Communication with any spacecraft in solar conjunction will be severely limited due to the sun's interference on radio transmissions from the spacecraft. When in reference to Satellite Communications, solar conjunction