diff --git a/src/central/adapters/firms.py b/src/central/adapters/firms.py
index 5d7cbc0..014a74b 100644
--- a/src/central/adapters/firms.py
+++ b/src/central/adapters/firms.py
@@ -2,6 +2,7 @@
 
 import csv
 import logging
+import math
 import sqlite3
 from collections.abc import AsyncIterator
 from datetime import datetime, timezone
@@ -51,6 +52,56 @@ SEVERITY_MAP = {
     "low": 1,
 }
 
+# 1° latitude ≈ 111 km everywhere; longitude scales by cos(lat).
+_KM_PER_DEG_LAT = 111.0
+# Defensive clamp: keeps cos(lat) bounded away from 0 at the poles. FIRMS
+# coverage stops well short of ±60°, so this only fires for malformed input.
+_POLE_CLAMP_DEG = 89.0
+
+
+def _pixel_polygon(
+    lat: float,
+    lon: float,
+    scan: float | None,
+    track: float | None,
+) -> dict[str, Any] | None:
+    """Build a rectangular GeoJSON Polygon for a FIRMS satellite pixel footprint.
+
+    scan and track are pixel dimensions in km from the FIRMS CSV. scan is the
+    along-track (~latitude) extent, track is the cross-track (~longitude)
+    extent; the cross-track dimension is scaled by cos(lat) to convert km to
+    degrees of longitude. Pixels are typically ~0.5×0.66 km at nadir and grow
+    off-nadir.
+
+    Returns None if scan or track is missing, non-numeric, or non-positive —
+    the caller falls back to centroid-only Geo.
+    """
+    if scan is None or track is None:
+        return None
+    try:
+        scan_km = float(scan)
+        track_km = float(track)
+    except (TypeError, ValueError):
+        return None
+    if scan_km <= 0 or track_km <= 0:
+        return None
+
+    clamped_lat = max(-_POLE_CLAMP_DEG, min(_POLE_CLAMP_DEG, lat))
+    half_scan_deg = (scan_km / 2.0) / _KM_PER_DEG_LAT
+    half_track_deg = (track_km / 2.0) / (
+        _KM_PER_DEG_LAT * math.cos(math.radians(clamped_lat))
+    )
+
+    # CCW ring with the closing vertex duplicated (GeoJSON requirement).
+    ring = [
+        [lon - half_track_deg, lat - half_scan_deg],
+        [lon + half_track_deg, lat - half_scan_deg],
+        [lon + half_track_deg, lat + half_scan_deg],
+        [lon - half_track_deg, lat + half_scan_deg],
+        [lon - half_track_deg, lat - half_scan_deg],
+    ]
+    return {"type": "Polygon", "coordinates": [ring]}
+
 
 class FIRMSSettings(BaseModel):
     """Settings schema for FIRMS adapter."""
@@ -313,9 +364,15 @@ class FIRMSAdapter(SourceAdapter):
         # Build stable ID
         stable_id = self._build_stable_id(satellite, acq_date, acq_time, lat, lon)
 
+        # Construct the satellite pixel footprint as a GeoJSON Polygon from
+        # scan/track. Falls back to centroid-only Geo if either dimension is
+        # missing/invalid — _build_geom_sql then stores a Point. We keep
+        # centroid alongside geometry so consumers that read only centroid
+        # still work.
+        geometry = _pixel_polygon(lat, lon, row.get("scan"), row.get("track"))
         geo = Geo(
             centroid=(lon, lat),  # GeoJSON order: lon, lat
-            bbox=(lon, lat, lon, lat),  # Point bbox
+            geometry=geometry,
             regions=[],
             primary_region=None,
         )
@@ -353,6 +410,10 @@ class FIRMSAdapter(SourceAdapter):
 
         total_features = 0
         total_new = 0
+        # Count emitted records that fell back to centroid-only Geo because
+        # scan/track were missing. Warned once at the end of the poll cycle
+        # rather than per-record to avoid log spam.
+        total_missing_dims = 0
 
         for satellite in self._satellites:
             url = self._build_url(satellite)
@@ -379,6 +440,8 @@ class FIRMSAdapter(SourceAdapter):
                         continue
 
                     event = self._row_to_event(row, satellite)
+                    if event.geo.geometry is None:
+                        total_missing_dims += 1
                     yield event
                     self.mark_published(stable_id)
                     new_count += 1
@@ -400,6 +463,15 @@ class FIRMSAdapter(SourceAdapter):
                 )
                 continue
 
+        if total_missing_dims:
+            logger.warning(
+                "FIRMS records missing scan/track — falling back to centroid-only Geo",
+                extra={
+                    "missing_count": total_missing_dims,
+                    "total_new": total_new,
+                },
+            )
+
         logger.info(
             "FIRMS poll completed",
             extra={
diff --git a/tests/test_firms.py b/tests/test_firms.py
index aafead2..55f7d15 100644
--- a/tests/test_firms.py
+++ b/tests/test_firms.py
@@ -1,5 +1,7 @@
 """Tests for FIRMS adapter."""
 
+import json
+import math
 import pytest
 from datetime import datetime, timezone
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -10,8 +12,10 @@ from central.adapters.firms import (
     FIRMSAdapter,
     CONFIDENCE_MAP,
     SATELLITE_SHORT,
+    _pixel_polygon,
 )
-from central.config_models import AdapterConfig, RegionConfig
+from central.archive import _build_geom_sql
+from central.config_models import AdapterConfig
 from central.models import Event, Geo
 
 
@@ -224,9 +228,12 @@ class TestEventGeneration:
         rows = adapter._parse_csv(SAMPLE_CSV, "VIIRS_SNPP_NRT")
         event = adapter._row_to_event(rows[0], "VIIRS_SNPP_NRT")
 
-        # GeoJSON order: lon, lat
+        # GeoJSON order: lon, lat. v0.9.21: degenerate point-bbox was dropped;
+        # the pixel footprint now ships as geo.geometry (Polygon).
         assert event.geo.centroid == (-116.456, 45.123)
-        assert event.geo.bbox == (-116.456, 45.123, -116.456, 45.123)
+        assert event.geo.bbox is None
+        assert event.geo.geometry is not None
+        assert event.geo.geometry["type"] == "Polygon"
 
 
 class TestDeduplication:
@@ -476,3 +483,123 @@ class TestEnrichmentIntegration:
 
         assert "_enriched" in event.data
         assert event.data["_enriched"]["geocoder"] == all_null_bundle()
+
+
+class TestPixelPolygon:
+    """v0.9.21: rectangular GeoJSON Polygon from FIRMS scan/track."""
+
+    def test_polygon_geometry_constructed(self):
+        """Happy path: realistic VIIRS scan/track -> CCW Polygon with closing vertex."""
+        # VIIRS at nadir: ~0.375km square; centroid should lie inside the ring.
+        geom = _pixel_polygon(lat=42.0, lon=-114.0, scan=0.375, track=0.375)
+        assert geom is not None
+        assert geom["type"] == "Polygon"
+        ring = geom["coordinates"][0]
+        # 4 corners + duplicated closing vertex
+        assert len(ring) == 5
+        assert ring[0] == ring[-1], "ring must close on its first vertex"
+        # CCW: signed area of the ring should be positive (lon=x, lat=y).
+        signed_area = sum(
+            (ring[i][0] * ring[i + 1][1]) - (ring[i + 1][0] * ring[i][1])
+            for i in range(len(ring) - 1)
+        )
+        assert signed_area > 0, "ring must wind counter-clockwise"
+        # Centroid is inside (axis-aligned rectangle, so min/max bounds check it).
+        lons = [pt[0] for pt in ring]
+        lats = [pt[1] for pt in ring]
+        assert min(lons) < -114.0 < max(lons)
+        assert min(lats) < 42.0 < max(lats)
+
+    def test_polygon_at_high_latitude(self):
+        """At lat=70°, longitude degrees stretch by 1/cos(70°) ≈ 2.92x."""
+        low = _pixel_polygon(lat=0.0, lon=0.0, scan=0.5, track=0.5)
+        high = _pixel_polygon(lat=70.0, lon=0.0, scan=0.5, track=0.5)
+        assert low is not None and high is not None
+
+        # half_track_deg at lat=70 should be ≈ 1/cos(70°) larger than at lat=0.
+        half_track_low = max(pt[0] for pt in low["coordinates"][0])
+        half_track_high = max(pt[0] for pt in high["coordinates"][0])
+        ratio = half_track_high / half_track_low
+        expected = 1.0 / math.cos(math.radians(70.0))
+        assert ratio == pytest.approx(expected, rel=1e-6)
+
+        # Latitude (scan) extent is independent of lat — same at both.
+        half_scan_low = max(pt[1] for pt in low["coordinates"][0])
+        half_scan_high = max(pt[1] for pt in high["coordinates"][0]) - 70.0
+        assert half_scan_low == pytest.approx(half_scan_high, rel=1e-9)
+
+    def test_pole_clamp(self):
+        """lat=89.99 must clamp to 89.0 instead of divide-by-near-zero."""
+        # Without clamping, cos(89.99°) ≈ 1.7e-4, blowing half_track_deg up
+        # to ~3000 deg. With the clamp at 89.0, cos(89°) ≈ 0.01745 keeps the
+        # polygon finite.
+        geom = _pixel_polygon(lat=89.99, lon=10.0, scan=0.5, track=0.5)
+        assert geom is not None
+        ring = geom["coordinates"][0]
+        half_track = max(pt[0] for pt in ring) - 10.0
+        expected = (0.5 / 2.0) / (111.0 * math.cos(math.radians(89.0)))
+        assert half_track == pytest.approx(expected, rel=1e-9)
+
+    def test_missing_scan_falls_back_to_point(self):
+        """scan=None must return None geometry (caller falls back to centroid)."""
+        assert _pixel_polygon(42.0, -114.0, None, 0.5) is None
+        assert _pixel_polygon(42.0, -114.0, 0.5, None) is None
+
+    def test_invalid_dims_fall_back(self):
+        """Non-numeric / non-positive scan or track must return None."""
+        assert _pixel_polygon(42.0, -114.0, "not-a-number", 0.5) is None
+        assert _pixel_polygon(42.0, -114.0, 0.0, 0.5) is None
+        assert _pixel_polygon(42.0, -114.0, -0.5, 0.5) is None
+
+
+class TestGeoGeometryRoundTripsThroughArchive:
+    """Regression guard: FIRMS geo.geometry must reach _build_geom_sql as Polygon."""
+
+    @pytest.mark.asyncio
+    async def test_geo_geometry_round_trips_through_archive_path(
+        self, temp_db_path, mock_config_store
+    ):
+        """Event with scan/track produces a Polygon SQL clause (mirrors tomtom_flow)."""
+        config = make_adapter_config()
+        adapter = FIRMSAdapter(
+            config=config,
+            config_store=mock_config_store,
+            cursor_db_path=temp_db_path,
+        )
+        rows = adapter._parse_csv(SAMPLE_CSV, "VIIRS_SNPP_NRT")
+        event = adapter._row_to_event(rows[0], "VIIRS_SNPP_NRT")
+
+        # Simulate what archive does: serialize geo to dict and run it through
+        # the same helper that produces the PostGIS geom clause.
+        geo_dict = event.geo.model_dump()
+        sql_clause = _build_geom_sql(geo_dict)
+        assert sql_clause is not None
+        decoded = json.loads(sql_clause)
+        assert decoded["type"] == "Polygon"
+        # Real footprint, not a degenerate point — first and third corners
+        # bracket the centroid in both axes.
+        ring = decoded["coordinates"][0]
+        assert ring[0] != ring[2]
+
+    @pytest.mark.asyncio
+    async def test_missing_dims_round_trips_as_point(
+        self, temp_db_path, mock_config_store
+    ):
+        """Without scan/track, archive still gets a usable Point geometry."""
+        config = make_adapter_config()
+        adapter = FIRMSAdapter(
+            config=config,
+            config_store=mock_config_store,
+            cursor_db_path=temp_db_path,
+        )
+        rows = adapter._parse_csv(SAMPLE_CSV, "VIIRS_SNPP_NRT")
+        # Strip scan/track to force fallback path.
+        rows[0]["scan"] = None
+        rows[0]["track"] = None
+        event = adapter._row_to_event(rows[0], "VIIRS_SNPP_NRT")
+        assert event.geo.geometry is None
+
+        geo_dict = event.geo.model_dump()
+        sql_clause = _build_geom_sql(geo_dict)
+        assert sql_clause is not None
+        assert json.loads(sql_clause)["type"] == "Point"