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Home , Heliosphere, Interstellar probe

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Using the to Decipher Exoplanet Signatures of Our from the Very Local Pontus C. Brandt, Ralph McNutt, Michael Paul, Carey Lisse, Kathleen Mandt, Abigail Rymer

The Decadal Survey Call for a future launch of the Interstellar Probe that in addition to it primary targets would offer valuable opportunities for exoplanetary research. Two seminal discoveries of the late 20th century fundamentally changed our perception of our home in space: the discovery in 1992 of Objects (KBOs), beginning with 15760 Albion [1], and the discovery in 1995 of planets beyond the (“exoplanets”) orbiting main sequence , beginning with 51 Pegasi b [2]. Following those discoveries, additional thousands of both types pf objects have been identified. The flyby of the Pluto system in 2014 [3] afforded us the first close up examination of a “free” KBO (allowing for the fact that ’s large moon Triton, observed from in 1989 [4], may be a “captured” one) and a second one with the smaller KBO 2014 MU69 planned for the first day of 2019. Exoplanets, by their at stellar distances, are not closely accessible with robotic , and the ongoing renaissance in our understanding of planetary systems is, therefore limited to remote, astronomical observations.

The “Interstellar Probe” into the nearby very local interstellar medium [5] (VLISM; within 0.01 parsec = 2,063 AU from the [6]) has been a mission of significant interest to the heliophysics community for some time [7, 8]. The most recent Heliophysics Decadal Survey calls for the future launch of the first dedicated Interstellar Probe (§10.5.2.7) [9], which would mark a historic milestone on NASA’s journey to the stars and would offer science discoveries of different proportions that will naturally bridge planetary, helio- and astrophysical disciplines by putting our solar system and in the context of the increasing number of other exoplanetary systems and astrospheres detected. While the primary target of the Interstellar Probe historically has been the characterization of the VLISM and implications for its interaction with the heliosphere, other targets include the circumsolar dust distribution and close imaging of unexplored Kuiper-Belt - 2 -

Objects, and the valuable opportunity to observe our own solar system as an exoplanetary system from a vantage up to 1000 AU from the Sun. This would allow: § The first external view of our heliosphere through (UV) and (ENA) imaging to place our own habitable astrosphere in the context of others. This would provide a reference to the nature of the stellar- of the host and its interaction with the surrounding exoplanets. § Understanding of the evolution of a , which is manifested in part by the large-scale distribution and motion of dust. Although dust emits in the infrared wavelengths, from a vantage point inside the solar system it is intrinsically difficult to determine its large-scale distribution. On its way outward, the Interstellar Probe can measure and determine the radial, compositional and size distribution of dust and provide a quantitative picture of the dust distribution that could be directly compared to the infrared (IR) observations of dust characterizing exoplanetary systems. § Use of transit observations of solar system planets from a vantage point far away from the Sun to develop a standard candle of transit observations of exoplanets.

To be more specific, and more focused on terrestrial and terrestrial-like planets, we note that comparative planetology combined with our detailed knowledge of our own inner solar system can be employed as a “gateway” to the exoplanets. By “comparative planetology” we mean the study of planetary processes, their manifestation, and their effects on multiple bodies, often using as a ‘baseline’, to understand the evolutionary pathways, similarities, and differences between planets. This refers to the sum of geology, hydrology, atmospheres/exospheres, surface processes, interior processes, , interactions with space, and, not least, habitability / biology (i.e., ). We may know most about the Earth, but the planets in our solar system give us context, improve understanding of our own , and provide baseline for understanding planets elsewhere.

The exoplanets are individual worlds, yet interconnected, and that can be compared with the inventory of planets within our own system. For example, the apparent increase in the minimum size of bodies with heliocentric distance is an observational bias - it is much harder to find small bodies at large geocentric distances. Similar biases in search for exoplanets constrain what we can find. Our own solar system and its bodies are imperfectly understood, and interiors, processes, even surfaces are still studied largely indirectly.

We have only one currently known system and planet that is habitable and inhabited with life, some of which, at least, is sentient. In practice in our looking at a growing “collection” of exoplanets, we are searching for other , or other ‘habitable’ worlds, with an expanded definition of habitable and conditions in both place and time. Our best understood example is not permanently stable. Earth’s past and future are hostile. Currently hostile planets may not have always been so, may not be completely so now. All the inner planets of our own system together and, in comparison, provide examples of likely pasts, futures, and presents among the exoplanets.

With the Voyagers now just escaping the heliosphere into near interstellar space, we have also found other mysteries that may affect habitability as well. The history of galactic cosmic rays and near supernova and other energetic events, while certainly rare, remain unknown, except though glimpses that may be provided by rare isotopic and compositional ratios in the near medium and - 3 - interstellar dust grains. Better understanding of these aspects of our environment along with the nature of the global interaction of the Sun with the VLISM have always been goals of an Interstellar Probe. Our new discovery of KBOs and exoplanets, long after the Voyagers “left the building” provide for the possibility of an interesting new perspective: using such a platform both to characterize the in-situ environment far from our star as well as to look back to see what habitability may look like from the nearby outside, and a habitability for which we know the answers already. Such an approach could very well help us better sort through the implications for life that can be gleaned from a growing body of knowledge about exoplanets.

References

[1] D. Jewitt, J. Luu, Discovery of the candidate Kuiper belt object 1992 QB1, Nature, 362 (1993) 730-732. [2] M. Mayor, D. Queloz, A -mass companion to a solar-type star, Nature, 378 (1995) 355-359. [3] S.A. Stern, F. Bagenal, K. Ennico, G.R. Gladstone, W.M. Grundy, W.B. McKinnon, J.M. Moore, C.B. Olkin, J.R. Spencer, H.A. Weaver, L.A. Young, T. Andert, J. Andrews, M. Banks, B. Bauer, J. Bauman, O.S. Barnouin, P. Bedini, K. Beisser, R.A. Beyer, S. Bhaskaran, R.P. Binzel, E. Birath, M. Bird, D.J. Bogan, A. Bowman, V.J. Bray, M. Brozovic, C. Bryan, M.R. Buckley, M.W. Buie, B.J. Buratti, S.S. Bushman, A. Calloway, B. Carcich, A.F. Cheng, S. Conard, C.A. Conrad, J.C. Cook, D.P. Cruikshank, O.S. Custodio, C.M. Dalle Ore, C. Deboy, Z.J.B. Dischner, P. Dumont, A.M. Earle, H.A. Elliott, J. Ercol, C.M. Ernst, T. Finley, S.H. Flanigan, G. Fountain, M.J. Freeze, T. Greathouse, J.L. Green, Y. Guo, M. Hahn, D.P. Hamilton, S.A. Hamilton, J. Hanley, A. Harch, H.M. Hart, C.B. Hersman, A. Hill, M.E. Hill, D.P. Hinson, M.E. Holdridge, M. Horanyi, A.D. Howard, C.J.A. Howett, C. Jackman, R.A. Jacobson, D.E. Jennings, J.A. Kammer, H.K. Kang, D.E. Kaufmann, P. Kollmann, S.M. Krimigis, D. Kusnierkiewicz, T.R. Lauer, J.E. Lee, K.L. Lindstrom, I.R. Linscott, C.M. Lisse, A.W. Lunsford, V.A. Mallder, N. Martin, D.J. McComas, R.L. McNutt, D. Mehoke, T. Mehoke, E.D. Melin, M. Mutchler, D. Nelson, F. Nimmo, J.I. Nunez, A. Ocampo, W.M. Owen, M. Paetzold, B. Page, A.H. Parker, J.W. Parker, F. Pelletier, J. Peterson, N. Pinkine, M. Piquette, S.B. Porter, S. Protopapa, J. Redfern, H.J. Reitsema, D.C. Reuter, J.H. Roberts, S.J. Robbins, G. Rogers, D. Rose, K. Runyon, K.D. Retherford, M.G. Ryschkewitsch, P. Schenk, E. Schindhelm, B. Sepan, M.R. Showalter, K.N. Singer, M. Soluri, D. Stanbridge, A.J. Steffl, D.F. Strobel, T. Stryk, M.E. Summers, J.R. Szalay, M. Tapley, A. Taylor, H. Taylor, H.B. Throop, C.C.C. Tsang, G.L. Tyler, O.M. Umurhan, A.J. Verbiscer, M.H. Versteeg, M. Vincent, R. Webbert, S. Weidner, G.E. Weigle, O.L. White, K. Whittenburg, B.G. Williams, K. Williams, S. Williams, W.W. Woods, A.M. Zangari, E. Zirnstein, The Pluto system: Initial results from its exploration by New Horizons, Science, 350 (2015). [4] E.C. Stone, E.D. Miner, The Voyager 2 encounter with the Neptune system, Science, 246 (1989) 1417-1421. [5] R.L. McNutt Jr, R.F. Wimmer-Schweingruber, Enabling interstellar probe, Acta Astronautica, 68 (2011) 790- 801. [6] R.L. McNutt Jr, M. Gruntman, S.M. Krimigis, E.C. Roelof, R.F. Wimmer-Schweingruber, Interstellar Probe: Impact of the Voyager and IBEX results on science and strategy, Acta Astronautica, 69 (2011) 767-776. [7] NRC, The Sun to the Earth -- and beyond: A decadal research strategy in solar and space , National Academies Press, Washington, D.C., 2003. [8] NRC, Exploration of the Outer Heliosphere and the Local Interstellar Medium: A Workshop Report, The National Academies Press, Washington, D. C., 2004. [9] NRC, Solar and Space Physics: A Science for a Technological Society National Academies Press, Washington, D.C., 2013. [10] C.S. Cockell, Life on Venus, Planetary and Space Science, 47 (1999) 1487-1501.