---
type: source
title: "Near-Surface Liquid Brines on Mars Inferred from Seasonal Marsquakes — Nature Communications 2025"
author: "Seismology research team (Nature Communications)"
url: https://www.nature.com/articles/s41467-025-67784-4
date: 2025-11-01
domain: space-development
secondary_domains: []
format: article
status: processed
processed_by: astra
processed_date: 2026-05-02
priority: high
tags: [mars, water, brines, marsquakes, ISRU, settlement, near-surface, northern-hemisphere]
intake_tier: research-task
extraction_model: "anthropic/claude-sonnet-4.5"
---

## Content

Published in Nature Communications (2025). Key findings:

**Core discovery:** Seasonal variations in marsquake frequency imply ice-to-brine phase transitions occurring at METER-SCALE DEPTHS in Mars' northern hemisphere (north of ~30°N).

**Mechanism:** During warmer seasons, subsurface ice melts to produce brines (salt-saturated liquid water). These brines lubricate fault zones, reducing frictional strength and triggering seasonal marsquakes. During colder periods, brines refreeze → marsquakes cease. The on-off pattern with seasonal temperature is the inversion signature.

**Depth characterization:**
- Brines confined to meter-scale depths (approximately 1-2m)
- Located north of ~30°N latitude in the northern hemisphere
- This is PRESENT-DAY liquid water activity, not ancient evidence

**Significance for settlement:**
- Mars water resources are not limited to polar ice caps or mid-latitude buried glaciers
- Northern hemisphere mid-latitudes have potentially harvestable brine at 1-2m depth, seasonally accessible
- Brine extraction at meter depths is an engineering challenge but not a physics prohibition
- Brines are salt-saturated (require desalination for potable use or electrolysis) — manageable with ISRU
- This is a NEW water access mode not previously in Astra's KB characterization

**Geographic zone:** Northern hemisphere above 30°N. This is the same zone as many proposed northern plains landing sites (Chryse Planitia, Utopia Planitia, Amazonis Planitia) but NOT the equatorial volcanic edifices (Tharsis, Elysium) where the best lava tubes are identified.

**Complementary paper:** Scientific Reports (2025) — RSL (recurring slope lineae) time-series compatible with contemporary water activity from bedrock aquifer melting, suggesting multiple independent water access modes may be active.

## Agent Notes
**Why this matters:** This directly addresses the Mars ISRU water question — the KB characterizes water access primarily as polar ice, with mid-latitude glaciers as secondary. Near-surface brines at meter depths in the northern hemisphere are a THIRD water access mode that is seasonally active today. This strengthens the settlement water ISRU case considerably.
**What surprised me:** The LIQUID water finding (not just ice). Previous paradigm: Mars water = polar ice caps + buried glaciers. Near-surface seasonal liquid brines are significantly more accessible than drilling for deep ice. The seasonal nature is manageable engineering.
**What I expected but didn't find:** Brine concentration data (how saline?). Desalination requirements will determine feasibility. The paper infers from seismology, not direct sampling.
**KB connections:** [[water is the strategic keystone resource of the cislunar economy because it simultaneously serves as propellant life support radiation shielding and thermal management]] (this claim is Moon-focused but the principle extends to Mars), the settlement health prerequisites from Vida's domain
**Extraction hints:** Primary claim: "Mars northern hemisphere near-surface brines (meter-scale depth, >30°N latitude) inferred from seasonal marsquake patterns represent a present-day liquid water access mode that expands Mars ISRU options beyond polar ice caps and buried glaciers." Confidence: experimental (seismological inference, not direct sampling).
**Context:** This is peer-reviewed Nature Communications — highest-credibility source. The code and dataset are on Zenodo (DOI available), meaning the analysis is reproducible.

## Curator Notes (structured handoff for extractor)
PRIMARY CONNECTION: [[water is the strategic keystone resource of the cislunar economy because it simultaneously serves as propellant life support radiation shielding and thermal management]] — claim was Moon-focused but Mars water ISRU is the parallel case
WHY ARCHIVED: First near-surface LIQUID water characterization with mechanism (seasonal brine) — this is a new category of Mars water resource, not just confirmation of known ice
EXTRACTION HINT: Two claims: (1) near-surface brines as third water access mode, (2) geographic constraint (>30°N limits co-location with equatorial lava tubes). Both are important for settlement planning.
