The Solar System:
The Solar System:
Mars
Mars
(Part III)
(Part III)
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Water (and life?) on Mars
Water (and life?) on Mars
There is definitely still water on Mars, frozen in the form of ice, even in regions away from the polar ice caps.
The real question, in terms of assessing the past and current possibilities for life to exist on Mars, is:
Is there liquid water on Mars?
Is there liquid water on Mars?
Evidence of current frozen water ice
Evidence of current frozen water ice
Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera acquired this image of the Phoenix Mars Lander hanging from its parachute as it descended to the Martian surface in 2008.
Credit (image and some text): NASA/JPL-Caltech/University of Arizona [link]
This artist's concept depicts NASA's Phoenix Mars Lander a moment before its 2008 touchdown on the arctic plains of Mars, in the north polar region. Pulsed rocket engines controlled the spacecraft's speed during the final seconds of descent. Phoenix's mission was to search for water.
Credit (image and some text): NASA/JPL-Calech/University of Arizona [link]
The Robotic Arm Camera on NASA's Phoenix Mars Lander captured this image underneath the lander on the fifth Martian day, or sol, of the mission. Descent thrusters on the bottom of the lander are visible at the top of the image.
This view from the north side of the lander toward the southern leg shows smooth surfaces cleared from overlying soil by the rocket exhaust during landing. The abundance of excavated smooth and level surfaces adds evidence to a hypothesis that the underlying material is an ice table covered by a thin blanket of soil.
Credit (image and some text): NASA/JPL-Caltech/University of Arizona/Max Planck Institute [link]These color images were acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (15 and 19 June 2008).
These images show sublimation of ice over the course of four days in a trench dug by Phoenix. Sublimation is direct evaporation (typically under low pressure conditions) from solid to gas form without passing through the liquid phase. On the Martian surface, water ice would be expected to sublimate instead of melting as it does on Earth. On Earth, carbon dioxide ice ("dry ice") sublimates directly into carbon dioxide gas.
In the lower left corner of the left image, a group of lumps is visible. In the right image, the lumps have disappeared, confirming that they were composed of water ice, not carbon dioxide ice (which would not have sublimated away).
This 12-meter-wide (39-foot-wide) crater in mid-latitude northern Mars was created by an impact that occurred between 3 July 2004 and 28 June 2008, as bracketed by before-and-after images not shown here. The images shown here were obtained by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter on 19 November 2008 (left) and 8 January 2009. The impact that dug the crater excavated water ice from below the surface. It is the bright material visible in this pair of images.
Evidence of vanished ancient liquid water on the surface of Mars
Evidence of vanished ancient liquid water on the surface of Mars
Dramatic flood events carved this impressive channel system on Mars. Called Kasei Valles, it covers 1.55 million square km, shown here in an image from ESA’s Mars Express.
Kasei Valles is one of the largest outflow channel systems on Mars – from source to sink, it extends some 3000 km and descends by 3 km in altitude. The channel originates beyond the southern (bottom) edge of this image near Valles Marineris, and empties into the vast plains of Chryse Planitia to the east (right).
Although it likely was carved by liquid water in the distant past, it is also possible that Kasei Valles was partially or totally carved by a lava flow.
Credit: ESA/DLR/FU Berlin (G. Neukum), CC BY-SA 3.0 IGO [link]
The same image of Kasei Valles colored to highlight topographic changes in height, from red/yellow colors at high altitude to blue/purple colors at low altitudes.
Credit: Institute of Geological Sciences at Freie Universität Berlin in cooperation with the DLR Institute of Planetary Research, Berlin [link]Ancient river channels emptying into a crater (former lake)?
Ancient river channels emptying into a crater (former lake)?
A Mars Odyssey spacecraft image of a large (14 km x 19 km) area of the Martian surface near Holden Crater, a 64 km wide crater whose northern edge is visible at the bottom of this image. A number of ancient flow channels (i.e., "river beds") are visible, with several leading into the smaller crater "Holden NE" (at upper right). The inset square outlined in white is shown in detail in the next figure.
Credit (image and some text): NASA/JPL/Malin Space Science Systems [link]
Detailed look at the floor of "Holden NE" Crater from the Mars Odyssey spacecraft image shown in the previous figure. Two ancient flow channels (rivers?) empty into the crater (a lake?) from the lower left corner and middle left side of this image. A "fossil" sediment distribution fan (a river delta?) emanating from these two channels spreads across the floor of the crater. The originally loose sediment in the channels of the fan has been turned to rock and then eroded over time to present the features seen today. The channels through which sediment was transported are no longer present; instead, only their floors have remained, and these have been elevated by erosion of the surrounding material so that former channels now stand as ridges. The floors of former channels became inverted because they were more resistant to the forces of erosion - either they were more strongly cemented than the surrounding materials, or they have more coarse grains (which are harder to remove), or both.
Credit (image and some text): NASA/JPL/Malin Space Science Systems [link]
Selenga River delta on the southeast shore of Lake Baikal, Russia. The fossil sediment distribution fan in "Holden NE" Crater on Mars is very similar in appearance to the same type of structure in an active river system on Earth.
Credit: "Earth As Art" satellite image courtesy of the USGS National Center for Earth Resources Observation and Science (EROS) and the National Aeronautics and Space Administration (NASA) Landsat Project Science Office [link]
Sedimentary rock in ancient (now dry!) lakebed. This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake. These rocks are interpreted to record sedimentation in a lake, as part of or in front of a delta, where plumes of river sediment settled out of the water column and onto the lake floor.This view spans about 1.5 meters (5 feet) across in the foreground. The color has been approximately white-balanced to resemble how the scene would appear under daytime lighting conditions on Earth.
Credit (image and some text): NASA/JPL-Caltech/MSSS [link]Evidence of current liquid (subsurface and surface) water
Evidence of current liquid (subsurface and surface) water
ESA’s Mars Express used radar signals bounced through underground layers of ice to find evidence of a pond of liquid water buried below the south polar cap of Mars.
The 200 km square study area is indicated in the left-hand image and the radar footprints on the surface are indicated in the middle image for multiple orbits. The greyscale background image is a Thermal Emission Imaging System image from NASA’s Mars Odyssey, and highlights the underlying topography: a mostly featureless plain with icy scarps in the lower right (south is up). The footprints are color-coded corresponding to the "power" of the radar signal reflected from features below the surface. The large blue area close to the center corresponds to the main radar-bright area, detected on many overlapping orbits of the spacecraft.
A subsurface radar profile is shown in the right hand panel for one of the Mars orbits. The bright horizontal feature at the top represents the icy surface of Mars in this region. The south polar layered deposits – layers of ice and dust – are seen to a depth of about 1.5 km. Below is a base layer that in some areas is even much brighter than the surface reflections, highlighted in blue, while in other places is rather diffuse. Analyzing the details of the reflected signals from the base layer yields properties that correspond to liquid water.
Credit (image and some text): Context map = NASA/Viking; THEMIS background = NASA/JPL-Caltech/Arizona State University; MARSIS data = ESA/NASA/JPL/ASI/Univ. Rome; R. Orosei, et al. (2018) [link]This time-lapse movie was assembled from images of the surface of Mars (Horowitz Crater in Terra Cimmeria) obtained by an orbiting satellite (MRO/HiRISE), and shows features called “recurring slope linae” – which basically just means “lines on a hill that keep reappearing”. These have been interpreted as surface water flowing downhill.
Possibilities for life on Mars?
Possibilities for life on Mars?
The 2015 science fiction movie The Martian, based on the novel of the same name, highlighted many of the difficulties humans would face trying to survive on Mars.
Just to be abundantly clear: this image is only meant to be funny! Bigfoot does not live on Mars! It's just a rock formation.
I mean, obviously - everyone knows Bigfoot lives in the Pacific Northwest on Earth.
OK {sigh} that last sentence was also just meant to be funny. I don't really think that there is a Bigfoot living anywhere. If you want to convince me, then show me the preponderance of verifiable, factual evidence that supports the existence of an unknown large hominid living among us.
Credit: assembled by D. W. Hoard (2018) from various internet sources that are extremely reliable (also a joke! really wish I didn't feel like I have to keep pointing that out!).
The Mars Orbiter Laser Altimeter (MOLA) aboard the Mars Global Surveyor produced the first global map of the topography of Mars. The Hellas Basin (large purple feature at about 60 degrees longitude in the southern hemisphere) is a giant impact basin like the maria on the Moon. It is 2300 km across and 9 km deep.
Hellas Basin is so deep that atmospheric pressure at the bottom is up to twice the Martian average. It would be possible for very salty water (brine) to exist as a surface (or near surface) liquid at the bottom of Hellas Basin.
Credit (image and some text): NASA/JPL/GSFC [link]
It is possible that the giant impact in Mars' past that “repaved” the northern hemisphere (see topographic map in previous figure) also disrupted the internal dynamo mechanism for generating Mars’ magnetic field and, therefore, led to the loss of most of Mars' atmosphere.
Mars only has a weak “fossil” magnetic field in located mainly in its southern hemisphere. This crustal magnetic field is 40 times weaker than Earth’s global magnetic field. It is produced by magnetized rocks in Mars' crust that formed and became magnetized before the internal dynamo mechanism ceased operating in Mars (because the core cooled and solidified and/or the core was disrupted by a giant impact).
The lack of a strong, global magnetic field presents a big problem for the survival of both native and immigrant life on Mars.
No protection from solar wind, cosmic rays, UV radiation = Bad health effects for DNA-based life
Credit: NASA [link]; also see Connerney, J. E. P. et al., 2005, Proceedings of the National Academy of Science (USA), 102, 14970 - "Tectonic implications of Mars crustal magnetism" [link]References
References
Lava origin for Kasei Valles
Leverington, D. W., 2017, Icarus, 301, 37 - “Is Kasei Valles (Mars) the largest volcanic channel in the solar system?” [link]
Giant impact repaved the northern hemisphere of Mars and destroyed its global magnetic field
Lakdawalla, E., 2008 (October 24), The Planetary Society - “Why is only half of Mars magnetized?” [link]
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