Scientists: Martian topography in one region suggests the past existence of lakes and river networks, but not a large single ocean
Based on a just published paper, scientists using orbital topography data and imagery have concluded that more than three billion years ago on Mars ancient rivers in the transition zone between the southern cratered highlands and the northern lowland plains fed into numerous lakes in the lowlands, not a single large ocean as some scientists posit.
From their abstract:
The northern third of Mars contains an extensive topographic basin, but there is conflicting evidence to whether it was once occupied by an ocean-sized body of water billions of years ago. At the margins of this basin are the remnants of deltas, which formed into water, but the size and nature of this water body (or water bodies) is unclear, and detailed investigations of different regions of the basin margins are necessary.
In this study, we use high-resolution image and topographic datasets from satellites orbiting Mars to investigate a series of water-formed landforms in the Memnonia Sulci region, set along the boundary of Mars’s northern basin. These landforms likely formed billions of years ago, providing evidence for ancient rivers and lakes in this region. The geologic evolution of these rivers and lakes was complicated, likely influenced by water-level fluctuations, changes in sediment availability, and impact cratering. Our topographic analysis of these rivers and lakes suggests that they terminated in a series of ancient lake basins at the boundary of Mars’s northern basin, rather than supplying a larger, ocean-sized body of water. [emphasis mine]
The Memnonia Sulci region is in the cratered highlands just south of the Medusae Fossae Formation, the largest volcanic ash deposit on Mars. The region of study in it is marked by the blue dot in the overview map to the right.
The study does not preclude the possible existence of a northern ocean on Mars, but it says that at least in this region at the equator, it did not exist. Instead, the various river valleys drained into separate smaller and relatively short-lived lakes.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Based on a just published paper, scientists using orbital topography data and imagery have concluded that more than three billion years ago on Mars ancient rivers in the transition zone between the southern cratered highlands and the northern lowland plains fed into numerous lakes in the lowlands, not a single large ocean as some scientists posit.
From their abstract:
The northern third of Mars contains an extensive topographic basin, but there is conflicting evidence to whether it was once occupied by an ocean-sized body of water billions of years ago. At the margins of this basin are the remnants of deltas, which formed into water, but the size and nature of this water body (or water bodies) is unclear, and detailed investigations of different regions of the basin margins are necessary.
In this study, we use high-resolution image and topographic datasets from satellites orbiting Mars to investigate a series of water-formed landforms in the Memnonia Sulci region, set along the boundary of Mars’s northern basin. These landforms likely formed billions of years ago, providing evidence for ancient rivers and lakes in this region. The geologic evolution of these rivers and lakes was complicated, likely influenced by water-level fluctuations, changes in sediment availability, and impact cratering. Our topographic analysis of these rivers and lakes suggests that they terminated in a series of ancient lake basins at the boundary of Mars’s northern basin, rather than supplying a larger, ocean-sized body of water. [emphasis mine]
The Memnonia Sulci region is in the cratered highlands just south of the Medusae Fossae Formation, the largest volcanic ash deposit on Mars. The region of study in it is marked by the blue dot in the overview map to the right.
The study does not preclude the possible existence of a northern ocean on Mars, but it says that at least in this region at the equator, it did not exist. Instead, the various river valleys drained into separate smaller and relatively short-lived lakes.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Where would the heat have come from for there to have been liquid water?
Once Mars had formed into a planet had the Sun also been fully formed? That is, its radiation output would be similar to what it puts out today? Meaning Mars would be freezing cold based on the heat it receives from the Sun.
If the heat needed to enable the water to be liquid came from the molten core of Mars, that liquid would evaporate to some degree, but then quickly turn to snow and ice once the gaseous water rises in the freezing Mars atmosphere?
After the early
Would that wate
Steve Richter:
Three billion years ago, the sun’s radiant power was even somewhat lower than it is today. If the planet had formed a solid crust some tens of millions of years after its formation, that crust acted as a very good thermal insulator. The heat flow from the interior was and is therefore much smaller than the energy flow from the sun. The reason why there was liquid water on the surface of Mars at that time is that the Martian atmosphere, due to its much higher density at the time, had a much stronger greenhouse effect and what led to a higher temperature of the Martian air. In addition, the heat in the air could be stored better because of the higher density, so that this Martian air did not cool down so much at night. Both led to a much higher temperature of the Martian air, despite the somewhat lower solar radiation at the time.
“… The reason why there was liquid water on the surface of Mars at that time is that the Martian atmosphere, due to its much higher density at the time, had a much stronger greenhouse effect and what led to a higher temperature of the Martian air. …”
And Mars has lost its atmosphere over time because it does not have enough gravity to keep it from escaping into space? If so, how was Mars able to condense from dust into a planet, but then lose the lighter stuff due to lack of gravity? IOW, the gases in the dust cloud condensed into the Mars atmosphere due to gravity, but then the planet loses those gases over time due to low gravity?
Steve Richter:
It takes a while for the initial atmosphere to be lost, probably mostly to the solar wind. This is a complex process, but one that still has an effect today.
https://www.youtube.com/watch?v=5V49yL4pe2E
Steve / Questioner
Can either of you speak to the lack of a magnetic field on Mars.
Gravity is not the determining factor on this one.
Wayne:
Here are my 2 cents: Both factors (magnetic field and gravitational field) play a role. A stronger magnetic field protects against the solar wind, or deflects large parts of it from the planet (earth for example). However, when the gravitational field is weak, the parts of the atmosphere ionized by the solar wind can escape more easily than on a planet with stronger gravity, since its escape velocity is faster. This is how the solar wind affects the atmosphere of Venus today, but it was only able to blow away relatively little, mainly the hydrogen produced when the water was split.
https://www.youtube.com/watch?v=9MVRMzmwubM
“… It takes a while for the initial atmosphere to be lost, probably mostly to the solar wind. This is a complex process, but one that still has an effect today. …”
That is fascinating. Deadly also. Without a magnetic field a planet cannot support life. Kind of like, to have life on a planet you first need intelligent life to visit the planet and put in place some mechanism which shields the planet from the solar wind.