MAL1c

One of the most fascinating questions in planetary science is how life originated on Earth and whether life exists beyond Earth. Life on Earth originated approximately 3.5 billion years ago and has adapted to nearly every explored environment including the deep ocean, dry deserts and ice continents. What were the chemical raw materials available for life to develop? Many carbonaceous compounds are identified by astronomical observations in our Solar System and beyond. Small Solar System bodies hold clues to both processes that formed our Solar System and the processes that probably contributed carbonaceous molecules and volatiles during the heavy bombardment phase to the young planets in our Solar System. The latter process may have contributed to life’s origin on Earth. Space missions that investigate the composition of comets and asteroids and in particular their organic content provide major opportunities to determine the prebiotic reservoirs that were available to early Earth and Mars. Recently, the Comet rendezvous mission Rosetta has monitored the evolution of comet 67P/Churyumov-Gerasimenko during its approach to the Sun. Rosetta observed numerous volatiles and complex organic compounds on the cometary surface and in the coma. JAXA’s Hayabusa-2 mission has returned samples from near-Earth asteroid Ryugu in December 2020 and we may have some interesting scientific results soon. Hayabusa-2 also carried the German-French landing module MASCOT (mobile asteroid surface scout) that provided new insights into the structure and composition of the asteroid Ryugu during its 17-hour scientific exploration.

Presently, a fleet of robotic space missions target planets and moons in order to assess their habitability and to seek biosignatures of simple extraterrestrial life beyond Earth. Prime future targets in the outer Solar System include moons that may harbor internal oceans such as Europa, Enceladus, and Titan. Life may have emerged during habitable periods on Mars and evidence of life may still be preserved in the subsurface, evaporite deposits, caves, or polar regions. On Mars, a combination of solar ultraviolet radiation and oxidation processes are destructive to organic material and life on and close to the surface. However, the progress and the revolutionary quality and quantity of data on “extreme life” on Earth has transformed our view of habitability. In 2021, we will hopefully have three robotic missions arriving at Mars from China, the United Arab Emirates and NASA (Tianwen-1, Hope, and Mars2020 respectively). In 2022, ESA’s ExoMars program will launch the Rosalind Franklin Rover and landing platform, and drill two meters deep into the Martian subsurface for the first time. Mars is still the central object of interest for habitability studies and life detection beyond Earth, paving the way for returned samples and human exploration.

Measurements from laboratory, field, and space simulations are vital in the preparation phase for future planetary exploration missions. This Cassini lecture will review the evolution and distribution of organic matter in space, including results from space missions, field and laboratory research, and discuss the science and technology preparation necessary for robotic and human exploration efforts investigating habitability and biosignatures in our Solar System.

How to cite: Ehrenfreund, P.: Organic chemistry in space and the search for life in our Solar System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16440, https://doi.org/10.5194/egusphere-egu21-16440, 2021.

The ionosphere of Mars is the conducting layer embedded within the thermosphere and exosphere that is mostly the result of solar EUV photoionization. It is also the layer that links the neutral atmosphere with space, and acts as the main obstacle to the solar wind. The ionosphere’s interaction with the solar wind is a critical aspect that determines the Martian atmospheric evolution, and ultimately the planet’s habitability. This interaction is often referred to as planetary Space Weather, the forecast of which is currently challenging due to the lack of a permanent in-situ solar wind monitor at Mars. Understanding the ionospheric response to solar wind variability is, therefore, essential in order to assess the response of the Martian plasma environment to the dissipation of energy from solar storms, and their impact on current technology deployed on the red planet.

This lecture will focus on our current knowledge of the Martian ionosphere. In particular, I will focus on our recent advances in the understanding of the Martian ionospheric reaction to different Space Weather events during the solar cycle, both from the data analysis and ionospheric modelling perspectives. Some important aspects to consider are the bow shock, magnetic pileup boundary, and ionopause characterization, as well as the behaviour of the topside and bottomside of the ionosphere taking into account the planet’s orbital eccentricity. Moreover, I will show the effect of electron precipitation from large Space Weather events in the very low Martian ionosphere, a region that it is not accessible to in-situ spacecraft observations. Finally, I will conclude the presentation by giving my perspective on some of the key outstanding questions that remain unknown, and I consider they constitute the next generation of Mars’ ionospheric science and exploration.

How to cite: Sanchez-Cano, B.: Mars’ ionosphere: from our current knowledge to the way forward, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5084, https://doi.org/10.5194/egusphere-egu21-5084, 2021.

While the term ‘space weather’ remains to some synonymous with operational anomalies on spacecraft, communications interruptions, and other practical matters, its broader implications extend across the EGU and beyond. Much of the science underlying space weather has to do with how our star, the Sun, affects the space environment at Earth’s orbit. We are lucky to be living at a time where information from both remote sensing (especially imaging at visible, x-ray and EUV wavelengths) and in-situ measurements (of plasmas, magnetic fields, and energetic particles) have provided unprecedented pictures of the Sun and knowledge of its extended atmosphere, the solar wind. Building on early forays into interplanetary space and deployments of coronagraphs with the Helios and SMM missions in the 70s and 80s, the Ulysses mission reconnaissance far above the ecliptic and the launch of Yohkoh’s and SOHO’s imagers in the 90s, and the long-term ‘monitoring’ of both the Sun and the conditions upstream of the Earth on SOHO, WIND and ACE, the STEREO mission opened a floodgate to research focused on solar activity and its heliospheric and terrestrial consequences. Physics-based, often semi-empirical 3D models increasingly came into widespread use for reconstructing and interpreting the multiple imaging perspectives and multipoint in-situ measurements that the twin STEREO spacecraft, combined with Earth-viewpoint assets (including the GONG ground-based network, and as of 2010, SDO magnetographs), provided on a regular basis. These observations and models together transformed perceptions of phenomena ranging from coronal structure to solar wind sources to eruptive phenomena and consequences, and the tools used to study and forecast them. Now Parker Solar Probe and Solar Orbiter are probing details of the still unexplored regions closer to the Sun than Mercury’s orbit, with the goal of completing that part of the solar/solar wind connection puzzle. And the overall science results from these observations and analysis efforts have not been confined to heliophysics, having especially influenced planetary science and astrophysics. They are seen in recreations of long-past scenarios when our Sun and solar system were evolving, in investigations of solar activity impacts including auroral emissions at the planets,  and in applications to distant planetary systems around other ‘Suns’. That these lofty implications are related to the bit flips and static ‘noise’ first identified with ‘space weather’, provides one of the interesting connections, and still ongoing journeys/stories, within EGU’s research universe.

How to cite: Luhmann, J. G.: The Science of Space Weather: From Bit Flips to Exoplanets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6488, https://doi.org/10.5194/egusphere-egu21-6488, 2021.

Coronal mass ejections (CMEs) are the most violent eruptions in the solar system. They are one of the main drivers of the heliospheric variability and cause various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). In general, interplanetary magnetic structures interact with GCRs producing depressions in the GCR flux. Therefore, different types of interplanetary magnetic structures cause different types of GCR depressions, allowing us to distinguish between them. In the interplanetary space the CME typically consists of two structures: the presumably closed flux rope and the shock/sheath which is formed ahead of the flux rope as it propagates and expands in the interplanetary space. Interaction of GCRs with these two structures is modelled separately, where the flux-rope related Forbush decrease can be modelled assuming that the GCRs diffuse slowly into the expanding flux rope, which is initially empty at its center (ForbMod model). The resulting Forbush decrease at a given time, i.e. heliospheric distance, reflects the evolutionary properties of CMEs. However, ForbMod is not yet able to take into account complex, non-self-similar evolution of the flux rope. Nevertheless, Forbush decreases can undoubtedly give us information on the CMEs in the heliosphere, especially where other measurements are lacking, and with further development, Forbush decrease reverse modelling could provide insight into the CME evolution.

How to cite: Dumbovic, M.: Utilizing galactic cosmic rays as signatures of coronal mass ejections, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-463, https://doi.org/10.5194/egusphere-egu21-463, 2021.