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
Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes
Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
17.01.2018 | Ecology, The Environment and Conservation
17.01.2018 | Physics and Astronomy
17.01.2018 | Awards Funding