NASA has been under the microscope of late, and the future of the manned space program is up for review. But that has not stopped NASA from creating an ambitious plan to explore our solar system using unmanned space craft.
The planet Venus is a dangerous place to explore. The temperatures on the surface of the rocky world reach 900 degrees Fahrenheit, making it the warmest body in our solar system besides the Sun. Such temperatures are enough to melt lead, making the proposition of landing a craft on the surface difficult.
The other difficulty with exploring the suface of Venus is the atmospheric pressure. Because of the thickness of the atmosphere it weighs down on the surface with a pressure 90 times greater than that on Earth. This is the same pressure that would be felt if you were submerged under 3,000 feet of water. (The deepest a person can safely dive underwater is less than 1100 feet without specialized suits and equipment. And even at those depths, special training is required, and is still considered quite risky due to the physiological effects on the body at those pressures.) Obviously this would all but prohibit landing humans on our neighboring world.
Since 1961 there have been 17 unmanned missions to "Earth's Sister" that have yielded great deals of information. However, no probe has lasted more than an hour on the surface, succombing to the immense heat and pressure. Recently, Russia proposed a return mission to Venus, but is garnering international support to defray the incredible costs. The goal is to have a probe -- or series of probes -- survive for at least 24 hours on the surface (one proposal even called for a 30 day exploration, but has falled out of favor due to the cost of such a mission).
Now, NASA is proposing its own mission. The Surface and Atmosphere Geochemical Explorer (SAGE) mission would take measurements of the atmosphere as it fell to the surface. This data would give scientists information about the atmospheric composition as well as details about the weather patterns that wreak havoc on the surface. Then, once on the ground, it would take samples of the soil and surface materials and beam the results of its analysis back to Earth. The hope is to understand what makes Venus so different from the other terrestrial worlds.
Returning to the Moon
The Moon has been in the news quite a bit as of late due to the recent unmanned mission to look for water beneath the surface, as well as proposals to send astronauts back to the surface. And NASA is looking at even more unmanned missions to our rocky companion.
The MoonRise probe is being designed to land in a large basin on the Moon's southern pole and collect rock samples (up to 2 pounds worth) and return them to Earth. The reason for the interest in such rocks is that it is believed that these rocks originated benearth the moon's crust in its mantle. Gathering and analyzing such rocks would give us great insights into the Moon's origins as well as valuable information about the evolution of our Solar System.
Land On An Asteroid
Perhaps the most unusual undertaking involves a proposal to land a craft on an asteroid passing by Earth. The Origins Spectral Interpretation Resource Identification Security Regolith Explorer (Osiris-Rex) would orbit and ultimately land on an asteroid.
Once on the surface, Osiris-Rex would gather up to 2 ounces of material from the asteroid and return them to Earth. While we have studied asteroids here on Earth, they are damaged by their fall through our atmosphere. This would give us an opportunity to study them in their purest form, and hopefully gain an understanding about the earliest days of our Solar System. The data may also help us understand how life formed through the examination of complex molecules in the rock.
Three Options, But Only Funding For One
While NASA would ultimately like to move all three projects forward, their budget only allows for one of them to move forward. Armed with about $650 million in funding (not including the cost to launch the probe), NASA is set to have one of these projects off the ground by the end of 2018.