Scientists call this work comparative planetology. Mars Express and Venus Express are so good at it because they carry very similar science instruments. In the case of the Analyser of Space Plasmas and Energetic Atoms (ASPERA), they are virtually identical. This allows scientists to make direct comparisons between the two planets.
The new results probe directly into the magnetic regions behind the planets, which are the predominant channels through which electrically-charged particles escape. They also present the first detection of whole atoms escaping from the atmosphere of Venus, and show that the rate of escape rose by ten times on Mars when a solar storm struck in December 2006.
By observing the current rates of loss of the two atmospheres, planetary scientists hope that they will be able to turn back the clock and understand what they were like in the past. “These results give us the potential to measure the evolution of planetary climates,” says David Brain, Supporting Investigator for plasma physics for Venus Express and Co-Investigator for ASPERA on Mars and Venus Express at the University of California, Berkeley.
The new observations show that, despite the differences in size and distance from the Sun, Mars and Venus are surprisingly similar. Both planets have beams of electrically charged particles flowing out of their atmospheres. The particles are being accelerated away by interactions with the solar wind, a constant stream of electrically charged particles released by the Sun.
At Earth, the solar wind does not directly interact with the atmosphere. It is diverted by Earth’s natural cloak of magnetism. Neither Mars nor Venus have appreciable magnetic fields generated inside the planet, so each planet’s atmosphere suffers the full impact of the solar wind.
Interestingly, this full-on interaction does create a weak magnetic field that drapes itself around each planet and stretches out behind the night-side in a long tail. Venus’s atmosphere is thick and dense, whereas that of Mars is light and tenuous. Despite the differences, the magnetometer instruments have discovered that the structure of the magnetic fields of both planets are alike.
“This is because the density of the ionosphere at 250 km altitude is surprisingly similar,” says Tielong Zhang, Principal Investigator for the Venus Express magnetometer instrument at Institut für Weltraumforschung (IWF), Österreiche Akademie der Wissenschaften, Austria. The ionosphere is the surrounding shell of electrically-charged particles created by the impact of sunlight on the planet’s upper atmosphere.
The proximity of Venus to the Sun does create an important difference, however. The solar wind thins out as it moves through space so the closer to the Sun it is encountered, the more concentrated is its force. This creates a stronger magnetic field, making the escaping atmospheric particles move collectively like a fluid.
At Mars, the weaker field means that the escaping particles act as individuals. “This is a fundamental difference between the two planets,” says Stas Barabash, ASPERA Principal Investigator on both Mars Express and Venus Express, Swedish Institute of Space Physics.
Another illuminating difference between Mars and Venus is that Mars displays strong small-scale magnetic fields locked into the crust of the planet. In some regions, these pockets protect the atmosphere, in others they actually help funnel the atmosphere into space.
The complexity of the different processes revealed at Venus and Mars means that planetary scientists do not yet have the full picture. “There will be many more results to come,” says Barabash.
There is a lot to do because there are many different mechanisms that may cause the atmospheric particles to escape. Untangling it all will take time. “The longer the spacecraft work together, the longer we can watch and see what really happens,” says Brain.
Håkan Svedhem | alfa
Argonne and CERN weigh in on the origin of heavy elements
31.03.2020 | DOE/Argonne National Laboratory
Physicist from Hannover Develops New Photon Source for Tap-proof Communication
30.03.2020 | Leibniz Universität Hannover
An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.
A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...
Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.
The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.
Researchers at the University of Zurich show that different stem cell populations are innervated in distinct ways. Innervation may therefore be crucial for proper tissue regeneration. They also demonstrate that cancer stem cells likewise establish contacts with nerves. Targeting tumour innervation could thus lead to new cancer therapies.
Stem cells can generate a variety of specific tissues and are increasingly used for clinical applications such as the replacement of bone or cartilage....
An international research team led by Kiel University develops an extremely porous material made of "white graphene" for new laser light applications
With a porosity of 99.99 %, it consists practically only of air, making it one of the lightest materials in the world: Aerobornitride is the name of the...
Researchers at Graz University of Technology have developed a framework by which wireless devices with different radio technologies will be able to communicate directly with each other.
Whether networked vehicles that warn of traffic jams in real time, household appliances that can be operated remotely, "wearables" that monitor physical...
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