# Sentence-Level Insights from the Martian Literature: A Natural Language Processing Approach
## 3 Results
### Unsupervised Clustering
\begin{table}
\begin{tabular}{c c c c} \hline
**No.** & **Sample Size** & **Topic** & **Summary** \\ \hline
26 & 349 & Evolution and Loss of Mars’ atmosphere & Mars’ atmosphere was once thicker, allowing liquid water. Solar wind stripping led to its current thin state. \\ \hline
27 & 340 & Martian Crustal Evolution and Composition & Mars’ crust formed through magma ocean processes. It is primarily basaltic with regional variations from volcanic and impact events. \\ \hline
28 & 311 & Subsurface and Ionospheric Sounding with MARSIS & Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) detects Mars’ subsurface structures and ionosphere, revealing buried ice, geological features, and dielectric properties. \\ \hline
29 & 306 & Perchlorates in Martian Soil and Their Implications & Perchlorates, found globally on Mars, form via atmospheric oxidation. They impact brine stability, habitability, and organic preservation. \\ \hline
30 & 305 & Aeolian Dunes on Mars: Morphology and Activity & Martian dunes are widespread, with varying activity. Orbital and rover data show migration, sediment transport, and climate influence. \\ \hline
31 & 304 & Mars-Solar Wind Interaction and Atmospheric Dynamics & Simulations show Mars’ interaction with the solar wind affects atmospheric escape and space weather, influenced by density changes and crustal fields. \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._
Research on the Martian surface was focused on geological landforms and mineral records shaped by possible liquid water activities, revealing the evolution of early climate changes and potential habitable environments. Sustained interest in this domain is reflected by the prominence of surface-related topics among the top ten research themes from 2001 to 2005 and from 2006 to 2010, with continued emphasis across subsequent periods. Specifically, between 2001 and 2005, studies based on MGS orbital remote sensing and Mars Exploration Rover (MER) field investigations identified geomorphic features and water-bearing minerals indicative of ancient liquid water activity, providing key evidence for past aqueous environments. From 2006 to 2010, research progressed toward  
Figure 4: Temporal evolution of Mars research hotspots based on unsupervised clustering. Clustering results are divided into five time periods: (**a**) 2001-2005, (**b**) 2006-2010, (**c**) 2011–2015, (**d**) 2016–2020, and (**e**) 2021–2024. The visualizations illustrate changes in topic distribution over time. Colored labels on the right indicate research themes summarized by the GPT-40 large model using the prompt: “Read the complete text and generate a short title.”  
integrating geological and climatic systems, focusing on water-rock interactions and CO\({}_{2}\) climate feedback mechanisms, and gradually constructing a framework for early Martian climate evolution. Between 2011 and 2015, attention shifted to sedimentary evolution and water storage processes, with empirical constraints strengthened through high-resolution observations, particularly in regions such as Gale Crater. From 2016 to 2020, research further deepened to investigate process mechanisms, including the relationship between wind systems and carbon cycling, and explored the role of an enhanced CO\({}_{2}\) + H\({}_{2}\) greenhouse effect on paleoclimate. Between 2021 and 2024, studies increasingly focused on the evolution of aeolian landforms and surface mineral diversity, examining the interactions between dust distribution and geomorphic changes to expand understanding of surface environments and paleoclimate evolution. Overall, research on the Martian surface has evolved from initial identification of morphological and aqueous indicators to in-depth analysis of process mechanisms and stratigraphic coupling, reflecting a progressive shift from discovery to interpretation in this field.