Mission
Delta-X monitors changes in the water, vegetation, and sediment along the Mississippi River Delta.
Travel with our Solar System Time Machine
By understanding the climate and geomorphology on other planets and moons of our Solar System, we can learn about our own Earth. Understanding other celestial bodies is like a time machine: We can look into possible past and future scenarios, as some are lacking greenhouse effects, and some experience too much.
Mississippi River Delta on Earth
Let's start with the Mississippi River Delta in the United States. It is growing and sinking in different areas, meaning some parts will be flooded, while others might experience droughts. Multiple missions, including the NASA Earth Venture Suborbital-3 mission "Delta-X" are used to monitor the area.
Duration
Delta-X is a 5-year mission that operates from 2019–2023
Observations
About the River Delta
The delta plain is a visible, broad, low-lying land mass where a river empties into a body of water. The sediment is transported to an open body of water (like the Gulf of Mexico) via distributary channels that stem off from the main river route. The remaining components become subaqueous and only the shallowest are visible in satellite imagery. Sediment type plays a major role in delta formation. Sediment in the Mississippi River Delta (MRD) is predominately sand, silt and clay, with sand being the coarsest and clay being the finest.
- A mouth bar is created when the distributary channel ends and water speed decreases, resulting in deposition of sediment.
- At the bottom of the slope is the delta front. The front is a shallow, subtidal portion of the delta where erosion and/or deposition and waves/tides are present.
- The prodelta is farther offshore and deeper below the influence of waves or tides. Here, sediment deposition is slowest and consists of the finer and lighter particles deposited from the river.
Clavius crater on the Moon
Our closest celestial body is our own Moon, so we will continue here!
Shadowed craters
In 2020, NASA announced the discovery of water on the sunlit surface of the Moon. Data from the Strategic Observatory for Infrared Astronomy (SOFIA), revealed that in Clavius crater, water exists in concentrations roughly equivalent to a 12-ounce bottle of water within a cubic meter of soil across the lunar surface. The discovery showed that water could be distributed across the lunar surface, even on sunlit portions, and not confined to cold, dark areas.
What can we learn from the Moon?
One of the sources for the moon's atmosphere is outgassing, the release of gases from the lunar interior, usually due to radioactive decay. Outgassing events may also occur during moonquakes. After being released, lighter gases escape into space almost immediately. Outgassing replenishes the tenuous atmosphere.
The impact of sunlight, the solar wind and micrometeorites hitting the moon's surface can also release gases that were buried in the lunar soil — a process called sputtering. These gases either fly off into space or bounce along the lunar surface. Sputtering may explain how water ice collected in lunar craters. Comets hitting the moon may have left some water molecules on the surface. Some of the molecules then accumulated in dark polar craters, forming beds of solid ice that some scientists and engineers have discussed mining for future human explorers.
Kraken Mare on Titan
Other than Earth, Saturn's moon Titan is the only known body in our solar system that appears to have surface lakes. Other than Earth, they are made of liquid Methane.
Astraeus Mission
Astraeus is our own mission proposal to explore both atmosphere, and lakes of Titan.
The mission architecture requires both, an orbital and a lander segment to meet the science objectives related to the atmosphere and lakes.
A Main Orbital Spacecraft (MOS) which comprises the major bus element will hold all other spacecraft. The MOS is also home to 2U CubeSats, called the Mites, that will analyse the upper atmosphere of Titan and how it changes with each season.
The major lander segments are an air vehicle (Mayfly) with a cable-deployed subsea vehicle (Manta). In-situ experiments of Titan's seas and lakes forms the primary objective of this mission but these bodies of hydrocarbons span approximately 68-85 degrees North. Geomophological features such as the connection between lakes and seas require aerial and subsea exploration. Therefore, the air and subsea vehicle (ASV) are operationally depenendent upon one another which is aided by a permenant mechanical link between the two vehicles via a data and power cable.
Cassini-Huygens Mission
Another mission is the Cassini-Huygens spacecraft. During a Cassini flyby in late February 2007, radar and camera observations revealed several large features in the north polar region interpreted as large expanses of liquid methane and/or ethane, including one, Ligeia Mare, with an area of 126,000 km2 (49,000 sq mi), slightly larger than Lake Michigan–Huron, the largest freshwater lake on Earth; and another, Kraken Mare, that would later prove to be three times that size. A flyby of Titan's southern polar regions in October 2007 revealed similar, though far smaller, lakelike features.
Surface lakes
There is an abundance of methane lakes, which are mainly concentrated near its southern and northern poles. Because methane exists as a liquid on Titan, it also evaporates and forms clouds, which occasionally causes methane rain. Clouds of methane ice and cyanide gas float over the moon's surface. Data also suggests the presence of a liquid ocean beneath the surface, but it is still to be confirmed.
What can we learn from Titan?
It is thought that conditions on Titan could make the moon more habitable in the far future. If the sun increases its temperature (6 billion years from now) and becomes a red giant star, Titan's temperature could increase enough for stable oceans to exist on the surface, according to some models. If this happens, conditions in Titan could be similar to Earth's, allowing conditions favorable for some forms of life.
Atmosphere of Venus
The next really interesting planet is our twin, Venus. We are lucky to be a bit further away from the Sun than our neighbour, since otherwise we might experience way greater greenhouse effects than we have on Earth.
The atmosphere of Venus
Venus has a thick atmosphere made up almost entirely of carbon dioxide. It also exerts a pressure 92 times higher than the Earth's, resulting in a pressure-cooker environment. Venus is covered by dense clouds made up primarily of sulfuric acid. The clouds are so thick it is impossible to see its surface without using sophisticated radar systems.
What can we learn from Venus?
One of the main reasons for heating is the clouds that form preferentially on the night side of the planet. These clouds cause a very powerful greenhouse effect. Simulations show that if Earth was just a little closer to the Sun, it could have gone down the same road as Venus. Laboratory experiments and evolutionary comparisons with its nearest neighbor, Earth, suggest that Venus once had liquid water as well as CO2 and nitrogen, but that water was lost early in evolution, perhaps due to its closer proximity to the Sun. The Earth has large stores of carbonates in its crust. The process of carbonate formation from CO2 gas proceeds more efficiently in the presence of liquid water, which first dissolves CO2 to form carbonic acid, which then affects the silicate minerals in rocks in contact with the ocean. By keeping the ocean with liquid water, Earth has gradually reduced the carbon dioxide content of its atmosphere. While both planets originally had atmospheres with high pressure and predominantly carbon dioxide (and high surface temperatures), CO2 on Earth ended up mostly in carbonate rocks, while on Venus it remained in the atmosphere.
Jezero crater on Mars
Our last celestial body we want to introduce and compare Earth to is Mars. Mars is a very interesting place for us human, beside our aim to have a permanent settlement, we can also learn a lot from the red planet. There is a possibility, that the Jezero crater is home to an ancient river delta, that was once flooded with water.
Salt-rich water
It was found that up to 15 meters below the surface of the crater floor, the material consists mainly of the magmatic mineral olivine and is layered by density and composition. The igneous composition of the rock indicates its volcanic origin, and the layering suggests that the material has been repeatedly exposed to liquid water. The lowest exposed geologic feature in the crater, known as the Séítah formation, was found to be predominantly composed of coarse crystalline olivine, while iron and magnesium carbonates detected in the material indicate reactions with carbon dioxide-rich water. The rocks also contain sulfates and perchlorates, which researchers believe were introduced later by evaporation of salt-rich water.
What can we learn from Mars?
Mars' atmosphere is over 100 times thinner than Earth's and is primarily composed of carbon dioxide, nitrogen and argon gases. Oxygized dust particles kicked up from the Martian surface fill the atmosphere turning Mars' skies a rusty tan color.
Water exists on Mars but the atmosphere is too thin for it to last long on the surface in a liquid state. Instead, water on Mars is found below the surface of the polar regions as water-ice and also as seasonal briny water flows down hillsides and crater walls. Reference
Furthermore, Scientists at Johns Hopkins University's Applied Physics Laboratory have discovered salt deposits less than 3 meters thick, deposited in shallow depressions on the gentle volcanic plains of Mars and formed as early as 2.3 billion years ago. “The closest analog we can find on Earth are chains of lakes that you get in Antarctica when snow melts seasonally atop permafrost,” Bethany Ehlmann, a Caltech professor of planetary science and co-author of the study, said in a statement. “It cannot penetrate deep into the frozen ground below, so when water evaporates, the salt deposit left behind is thin.” Reference.